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2011 latest J2ME Projects - JAVA

2011-02-06T12:31:00.000-08:00

2011 latest J2ME Projects - JAVA

     Share your J2me Project ideas through comments
   share your knowledge and help others
   Share your data and project codes through comments

ProjectName	Study on Travel Route Intelligent Navigation System Based on WEBGIS
Abstract	this paper presents the system architecture, key technology and system realization for the travel route intelligent navigation system based on WEBGIS. Combining with Oracle spatial database and MapXtreme technology and using comprehensively position service, GIS and data mining and according to the traveler’s type, preference, characteristics and requirement, the system can provide user information management, intelligent information processing and travel route planning services intelligently and personally.
Domains	Web Data Mining, WEBGIS, GIS, MaxExtreme.
Keywords	web gis; tourism; travel route planning; travel route navigation
H/w & S/w	Java, J2ME.

ProjectName	Speedy, Mini and Totally Fuzzy: Three Ways for Fuzzy Sequential Patterns Mining
Abstract	Most real world databases are constituted from historical and numerical data such as sensors, scienti c or even demographic data. In this context, algorithms extracting sequential patterns, which are well adapted to the temporal aspect of the data, do not allow processing numerical information. Therefore the data are pre-processed to be transformed into a binary representation which leads to a loss of information. Algorithms have been proposed to process numerical data using intervals and particularly fuzzy intervals. With regards to the search of sequential patterns based on fuzzy intervals, both existing methods are incomplete either in the processing of sequences or in the support computation. Therefore this paper proposes three methods to mine fuzzy sequential patterns (SPEEDYFUZZY MINIFUZZY and TOTALLYFUZZY). We detail these algorithms by highlighting their different fuzzi cation levels.
Domains	Fuzzy Sequential Pattern, Data Minining
Keywords	SPEEDYFUZZY, MINIFUZZY
H/w & S/w	Java,Windows/Linux

ProjectName	Automatic Form Filling on Mobile Devices
Abstract	Filling out forms of web based services on mobile devices is a very time consuming and frustrating task for users because of the limited text input capabilities. This is a critical point to get a wide acceptance of such services, especially mobile commerce that often requires filling user data. We developed an architecture based on a local proxy on a mobile device and a lightweight algorithm for a comprehensive analysis of forms, which leads to the highest probable user data to be filled in, driven by an initial rule set [1]. We further discuss our implementation and the evaluation results of the algorithm as well as the usability of the prototype.
Domains	J2ME, J2SE
Keywords	Mobile, NTT DoCoMo, PDA,
H/w & S/w	Java,Windows/Linux

ProjectName	Optimal resource allocation on grid systems for maximizing service reliability using a genetic algorithm
Abstract	Grid computing system is different from conventional distributed computing systems by its focus on large-scale resource sharing and open architecture for services. The global grid technologies and the Globus Toolkit in particular, are evolving toward an open grid service architecture (OGSA) with which a grid system provides an extensible infrastructure so that various organizations can offer their own services and integrate their resources. Hence, this paper aims at solving the problem of optimally allocating services on the grid tomaximize the grid service reliability. Since no existing study has analyzed the grid service reliability, this paper develops initial modeling and evaluation algorithms to evaluate the grid service reliability. Based on the grid service reliability evaluation, we present an optimization model for the grid service allocation problem and develop a genetic algorithm (GA) to effectively solve it. A numerical example is given to show the modeling procedures and efficiency of the GAs.
Domains	Grid Computing, Open grid servic architecture
Keywords	Grid service reliability; Genetic algorithm; Graph theory; Optimization; Resource management
H/w & S/w	Java,windows/Linux

ProjectName	Web Service Composition in UML
Abstract	As the number of available web services is steadily increasing, there is a growing interest for reusing basic web services in new, composite web services. Several organizations have proposed composition languages (BPML, BPMN, BPEL4WS, BPSS, WSCI), but no winner has been declared so far. This paper proposes a method that uses UML Activity models to design web service compositions, and OMG's Model Driven Architecture (MDA) to generate executable specifications in different composition languages. The method utilizes standard UML constructs with a minimal set of extensions for web services. An important step in the method is the transformation of WSDL descriptions into UML. This information is used to complete the composition models.Another key aspect of the method is its independence of the web service composition language. The user can thus select his preferred composition language.
Domains	Web Service,UML
Keywords	BPML, BPMN, BPEL4WS, BPSS, WSCI, WSDL, WorkSCo
H/w & S/w	Java,Windows/Linux

ProjectName	Ping Identity over the cloud computing
Abstract	Now days, the mechanism of ping identity is widely in order to provide the security and digital identity to the important products. Thus the services of ping identity means the digital identity management are crucial in order to authenticate the users and providing the dynamic access control to services in the infrastructures of cloud computing. These kinds of mechanisms are mostly based on the properties of user identity and histories of past interactions. This services needs to preserve the user’s privacy, during the same time enhancing the multiple domains interoperability and simplifying the identity verification management. Therefore in this proposed research work, we are introducing the new methods and approaches in order to address such requirement which is based on the policies for the high level verification presented in terms of protocols of zero knowledge proof, identity attributes, techniques of semantic matching etc. Our main aim is to design the architecture with the proposed basic techniques and analyze the performance results for the same.
Domains	Cloud Computing, Ping Idenity
Keywords	Users Privacy, Zero Knowledge proof, Web Policies
H/w & S/w	Java and Ms-Sqlserver

ProjectName	Java Based Intelligent Drip Irrigation Control
Abstract	This project defines the implementation of a Java driven intelligent and completely automated drip irrigation system. The software and hardware combined together provide a very advanced control over the currently implemented manual system. The implementation involves use of valve control, drip control and pump control using a microcontroller based board. The java driven software is used to interface and control the valve timings. An additional ADC board is provided to collect moisture level feedback from various regions of the field. This helps the user in collecting different feedback from different areas of the field where separate breeds of crops can be cultivated accordingly.
Domains	Networking Based
Keywords	ADC board
H/w & S/w	Java

ProjectName	Mobile Based Remote Process Control
Abstract	This project describes mobile remote hardware control architecture. It is very suitable for industries, remote laboratories, etc. The idea is to set up a central terminal equipped with a GSM Modem at the industry/laboratory, which can be used to transmit/receive data and/or commands to and from the administrator/s. The data can be anything from boiler temperature to gas concentration values, etc. and the commands can be anything from Relay on/off to Motor control, speed control, PWM control, threshold setting, etc. The entire process control job can be made remote using this architecture.
Domains	Mobile Computing
Keywords	STP,T145,GSM,PWM control.
H/w & S/w	Java,J2ME

ProjectName	Enforcing Minimum-Cost Multicast Routing against Selfish Information Flows
Abstract	We study multicast in a noncooperative environment where information flows selfishly route themselves through the cheapest paths available. The main challenge is to enforce such selfish multicast flows to stabilize at a socially optimal operating point incurring minimum total edge cost, through appropriate cost allocation and other economic measures, with replicable and encodable properties of information flows considered. We show that known cost allocation schemes are not sufficient. We provide a shadow-price-based cost allocation for networks without capacity limits and show that it enforces minimum-cost multicast. This improves previous result where a approximate multicast flow is enforced. For capacitated networks, computing cost allocation by ignoring edge capacities will not yield correct results. We show that an edge tax scheme can be combined with a cost allocation to strictly enforce optimal multicast flows in this more realistic case. If taxes are not desirable, they can be returned to flows while maintaining weak enforcement of the optimal flow. We relate the taxesto VCGpaymentschemesand discussan efficientprimal-dualalgorithmthatsimultaneously computesthe taxes,the cost allocation, and the optimal multicast flow, with potential of fully distributed implementations.
Domains	Parallel & Distributed Systems
Keywords	LP Formulations, Primal & Dual, Communication/networking, multicast, graph algorithms.
H/w & S/w	java with windows/Linux

ProjectName	Encrypted Voice Calls with IP enabled Wireless Phones over GSM/ CDMA/ WiFi Networks
Abstract	A research on the related technology and implementation of IP phone based on WiFi network is discussed in this paper; it includes the net structure of the technology used in designing the terminal of IP phone. This technology is a form of telecommunication that allows data and voice transmissions to be sent across a wide range of interconnected networks. A WiFi enabled IP phone is used which is preinstalled with the Symbian Operating System and a software application is developed using J2ME which allows free and secured communication between selected IP phones in the WiFi network. This communication is done with the use of routing tables organized in the WiFi routers. Using the free bandwidth of 2.4 GHz communication channels are established. The communication channel being a free bandwidth is vulnerable to external attacks and hacking. Thereby this challenge of creating a secure communication channel is addressed by using two different encryption mechanisms. The payload and header of the voice data packets encrypted using two different algorithm techniques. Hence the communication system is made almost fully secure. Also the WiFi server can tunnel the calls to the GSM network using UNC. Moreover the creation of a vertical handoff protocol will provide seamless communication for users. This handoff is defined in the context of a diverse network environment. It is cost effective, it allows easier communication, is great for international usages, and it can be very useful for large corporations. In time this will become a cheap and secure way to communicate and will have a large effect on university, business and personal communication.
Domains	Mobile Computing, Network Security.
Keywords	IP phones, Wifi ,Symbian, J2ME, encryption, GSM,UNC.
H/w & S/w	Java with windows/Linux

ProjectName	Remote Surveillance and Face Tracking with Mobile Phones (Smart Eyes)
Abstract	This thesis addresses analysis, evaluation and simulation of low complexity face detection algorithms and tracking that could be used on mobile phones. Network access control using face recognition increases the user-friendliness in human-computer interaction. In order to realize a real time system implemented on handheld devices with low computing power, low complexity algorithms for face detection and face tracking are implemented. Skin color detection algorithms and face matching have low implementation complexity suitable for authentication of cellular network services. Novel approaches for reducing the complexities of these algorithms and fast implementation are introduced in this thesis. This includes a fast algorithm for face detection in video sequences, using a skin color model in the HSV (Hue-Saturation-Value) color space. It is combined with a Gaussian model of the H and S statistics and adaptive thresholds. These algorithms permit segmentation and detection of multiple faces in thumbnail images. Furthermore we evaluate and compare our results with those of a method implemented in the Chromatic Color space (YCbCr). We also test our test data on face detection method using Convolutional Neural Network architecture to study the suitability of using other approaches besides skin color as the basic feature for face detection. Finally, face tracking is done in 2D color video streams using HSV as the histogram color space. The program is used to compute 3D trajectories for a remote surveillance system.
Domains	Mobile Computing, Intelligant Systems, J2ME.
Keywords	Remote Surveillance, Face Tracking, Mobile Phones, Face Detection, HSV Color Space, Face Recognition, Color Histogram, Skin Color Pixel, intensity gradient.
H/w & S/w	java with windows/Linux

ProjectName	Grid Banking System Structure
Abstract	Highly computational resource sharing environments like grids pose major security issues. Secure interoperability has been a growing concern for such multi domain computing systems. Collaboration in such a diverse environment requires integration of all local policies to compose a global access control policy for controlling information and resource. Access control in such an environment is still an open problem. The much standardized Role Based Access Control (RBAC) is yet to be fully utilized in a multi domain grid environment like the Grids. Here, we present an architectural framework for adaptation and implementation of RBAC for grid access control. Our approach includes solutions for delegation and revocation in a single domain grid enterprise like bank. The classical Role Based Access Control, though an effective access control standard, does not address the issue of resolving a local role into a global role. So, we also propose architecture based on RBAC, which can establish role equivalence among the domains by mapping a local domain role to its equivalent global role. We use the approach of weighted ranking for the same. The final authorization decision is made based on the mapped global role ranking. And also the resource access policies.
Domains	Grid Banking, Grid Computing.
Keywords	Role Based Access Control, Grid Banking, resource sharing, authorization policies.
H/w & S/w	java with windows 2000 onwards and Linux,SQL server 2000 onwards

ProjectName	A Role and Attribute Based Access Control System Using Semantic Web Technologies
Abstract	We show how Semantic Web technologies can be used to build an access control system. We follow the role-based access control approach (RBAC) and extend it with contextual attributes. Our approach provides for the dynamic association of roles with users. A Description Logic (DL) reasoner is used to classify both users and resources, and verify the consistency of the access control policies. We mitigate the limited expressive power of the DL formalism by refining the output of the DL reasoner with SPARQL queries. Finally, we provide a proof-ofconcept implementation of the system written in Java
Domains	Web Based Collaboration, Authorization Models
Keywords	RBAC (Role based access control), ABAC (Attribute Based access control),
H/w & S/w	Java, J2ME, windows/Linux

ProjectName	A Fully Automatic CAD-CTC System Based on Curvature Analysis for Standard and Low-Dose CT Data
Abstract	Computed tomography colonography (CTC) is a rapidly evolving noninvasive medical investigation that is viewed by radiologists as a potential screening technique for the detecby radiologists as a potential screening technique for the detection of colorectal polyps. Due to the technical advances in CT system design, the volume of data required to be processed by radiologists has increased significantly, and as a consequence the manual analysis of this information has become an increasingly time consuming process whose results can be affected by inter time consuming process whose results can be affected by interand intrauser variability. The aim of this paper is to detail the implementation of a fully integrated CAD-CTC system that is able to robustly identify the clinically significant polyps in the CT data.The CAD-CTC system described in this paper is a multistage implementation whose main system components are: 1) automatic colon segmentation; 2) candidate surface extraction; 3) feature extraction; and 4) classification. Our CAD-CTC system performs at 100% sensitivity for polyps larger than 10 mm, 92% sensitivity for polyps in the range 5 to 10 mm, and 57.14% sensitivity for polyps smaller than 5 mm with an average of 3.38 false positives per dataset. The developed system has been evaluated on synthetic and real patient CT data acquired with standard and low-dose radiation levels.
Domains	Image Processing.
Keywords	Classification, computed tomography (CT), convexity
H/w & S/w	java,windows/Linux

ProjectName	Patient Centric Medical Information System using Web Services
Abstract	This Software Requirements Specification provides a complete description of all the functions and specifications for the purpose of the project on Patient Centric Medical Information System Using Web Services. This Medical Information System deals with the Tuberculosis related data for the patients provided by means of Web Services. This system is beneficial for use mainly by the outdoor patients and medical professionals.
Domains	Web Services
Keywords	Proxy Server,Web Portal.
H/w & S/w	Java,J2ME.windows/Linux

ProjectName	E-Learning as a Web Service
Abstract	E-learning has been a topic of increasing interest in recent years. It is often perceived as a group effort, where content authors, instructional designers, multimedia technicians, teachers, trainers, database administrators, and people from various other areas of expertise come together in order to serve a community of learners On the other hand, there are increasingly many activities which aim at providing services of any kind on the Web [9]; these can occur as business-tobusiness or as business-to-consumer services and are generally subsumed under the term Web services. In this paper we suggest to combine the areas of e-learning and Web services, by providing electronic learning offerings as (individual ) Web services as well. We elaborate on this by showing how content providers and content consumers (i.e., learners) can communicate appropriately through a Web service platform with its common description publication, and retrieval functionalities. Finally, we indicate how a corresponding system can be realized.
Domains	Web Services
Keywords	SOAP, WDSL, UML, BPEL.
H/w & S/w	Java,J2ME.Windows/Linux

2011 latest J2SE Projects - JAVA

2011-02-06T12:20:00.000-08:00

2011 latest J2SE Projects - JAVA

   Share your J2Se Project ideas through comments
   share your knowledge and help others
   Share your data and project codes through comments

ProjectName	Advanced Star Coordinates
Abstract	With the development of data collection technology,effective visualization tools are needed urgently to understand the abundant multidimensional and multivariate data and information in the science,engineering and commerce fields. Star Coordinates is a traditional multivariate data visualization technique,but there are some limitations of it. In the paper we propose the Advanced Star Coordinates (ASC), which addresses these drawbacks. ASC uses the diameter instead of the radius as the dimension axis, projects the multidimensional information object to low dimension visual space, which is meaningful to users, and designs the dimension configuration strategy to optimize the order and angle of the dimension axes. The experiment results show that the dimension configuration strategy reduces the user operation burden greatly and helps them explore the connotative characteristics of the multidimensional information aggregation quickly and exactly. The visualization result is easily understandable and expresses the dimension distribution information effectively.
Domains	Data Mining, Data Processing.
Keywords	Star coordinates,data visualization
H/w & S/w	java

ProjectName	Study on Travel Route Intelligent Navigation System Based on WEBGIS
Abstract	this paper presents the system architecture, key technology and system realization for the travel route intelligent navigation system based on WEBGIS. Combining with Oracle spatial database and MapXtreme technology and using comprehensively position service, GIS and data mining and according to the traveler’s type, preference, characteristics and requirement, the system can provide user information management, intelligent information processing and travel route planning services intelligently and personally.
Domains	Web Data Mining, WEBGIS, GIS, MaxExtreme.
Keywords	web gis; tourism; travel route planning; travel route navigation
H/w & S/w	Java, J2ME.

ProjectName	Speedy, Mini and Totally Fuzzy: Three Ways for Fuzzy Sequential Patterns Mining
Abstract	Most real world databases are constituted from historical and numerical data such as sensors, scienti c or even demographic data. In this context, algorithms extracting sequential patterns, which are well adapted to the temporal aspect of the data, do not allow processing numerical information. Therefore the data are pre-processed to be transformed into a binary representation which leads to a loss of information. Algorithms have been proposed to process numerical data using intervals and particularly fuzzy intervals. With regards to the search of sequential patterns based on fuzzy intervals, both existing methods are incomplete either in the processing of sequences or in the support computation. Therefore this paper proposes three methods to mine fuzzy sequential patterns (SPEEDYFUZZY MINIFUZZY and TOTALLYFUZZY). We detail these algorithms by highlighting their different fuzzi cation levels.
Domains	Fuzzy Sequential Pattern, Data Minining
Keywords	SPEEDYFUZZY, MINIFUZZY
H/w & S/w	Java,Windows/Linux

ProjectName	Automatic Form Filling on Mobile Devices
Abstract	Filling out forms of web based services on mobile devices is a very time consuming and frustrating task for users because of the limited text input capabilities. This is a critical point to get a wide acceptance of such services, especially mobile commerce that often requires filling user data. We developed an architecture based on a local proxy on a mobile device and a lightweight algorithm for a comprehensive analysis of forms, which leads to the highest probable user data to be filled in, driven by an initial rule set [1]. We further discuss our implementation and the evaluation results of the algorithm as well as the usability of the prototype.
Domains	J2ME, J2SE
Keywords	Mobile, NTT DoCoMo, PDA,
H/w & S/w	Java,Windows/Linux

ProjectName	Optimal resource allocation on grid systems for maximizing service reliability using a genetic algorithm
Abstract	Grid computing system is different from conventional distributed computing systems by its focus on large-scale resource sharing and open architecture for services. The global grid technologies and the Globus Toolkit in particular, are evolving toward an open grid service architecture (OGSA) with which a grid system provides an extensible infrastructure so that various organizations can offer their own services and integrate their resources. Hence, this paper aims at solving the problem of optimally allocating services on the grid tomaximize the grid service reliability. Since no existing study has analyzed the grid service reliability, this paper develops initial modeling and evaluation algorithms to evaluate the grid service reliability. Based on the grid service reliability evaluation, we present an optimization model for the grid service allocation problem and develop a genetic algorithm (GA) to effectively solve it. A numerical example is given to show the modeling procedures and efficiency of the GAs.
Domains	Grid Computing, Open grid servic architecture
Keywords	Grid service reliability; Genetic algorithm; Graph theory; Optimization; Resource management
H/w & S/w	Java,windows/Linux

ProjectName	Web Service Composition in UML
Abstract	As the number of available web services is steadily increasing, there is a growing interest for reusing basic web services in new, composite web services. Several organizations have proposed composition languages (BPML, BPMN, BPEL4WS, BPSS, WSCI), but no winner has been declared so far. This paper proposes a method that uses UML Activity models to design web service compositions, and OMG's Model Driven Architecture (MDA) to generate executable specifications in different composition languages. The method utilizes standard UML constructs with a minimal set of extensions for web services. An important step in the method is the transformation of WSDL descriptions into UML. This information is used to complete the composition models.Another key aspect of the method is its independence of the web service composition language. The user can thus select his preferred composition language.
Domains	Web Service,UML
Keywords	BPML, BPMN, BPEL4WS, BPSS, WSCI, WSDL, WorkSCo
H/w & S/w	Java,Windows/Linux

ProjectName	Ping Identity over the cloud computing
Abstract	Now days, the mechanism of ping identity is widely in order to provide the security and digital identity to the important products. Thus the services of ping identity means the digital identity management are crucial in order to authenticate the users and providing the dynamic access control to services in the infrastructures of cloud computing. These kinds of mechanisms are mostly based on the properties of user identity and histories of past interactions. This services needs to preserve the user’s privacy, during the same time enhancing the multiple domains interoperability and simplifying the identity verification management. Therefore in this proposed research work, we are introducing the new methods and approaches in order to address such requirement which is based on the policies for the high level verification presented in terms of protocols of zero knowledge proof, identity attributes, techniques of semantic matching etc. Our main aim is to design the architecture with the proposed basic techniques and analyze the performance results for the same.
Domains	Cloud Computing, Ping Idenity
Keywords	Users Privacy, Zero Knowledge proof, Web Policies
H/w & S/w	Java and Ms-Sqlserver

ProjectName	Java Based Intelligent Drip Irrigation Control
Abstract	This project defines the implementation of a Java driven intelligent and completely automated drip irrigation system. The software and hardware combined together provide a very advanced control over the currently implemented manual system. The implementation involves use of valve control, drip control and pump control using a microcontroller based board. The java driven software is used to interface and control the valve timings. An additional ADC board is provided to collect moisture level feedback from various regions of the field. This helps the user in collecting different feedback from different areas of the field where separate breeds of crops can be cultivated accordingly.
Domains	Networking Based
Keywords	ADC board
H/w & S/w	Java

ProjectName	Mobile Based Remote Process Control
Abstract	This project describes mobile remote hardware control architecture. It is very suitable for industries, remote laboratories, etc. The idea is to set up a central terminal equipped with a GSM Modem at the industry/laboratory, which can be used to transmit/receive data and/or commands to and from the administrator/s. The data can be anything from boiler temperature to gas concentration values, etc. and the commands can be anything from Relay on/off to Motor control, speed control, PWM control, threshold setting, etc. The entire process control job can be made remote using this architecture.
Domains	Mobile Computing
Keywords	STP,T145,GSM,PWM control.
H/w & S/w	Java,J2ME

ProjectName	2D/3D Web Content Visualization Toolkit
Abstract	This project describes a three-dimensional search engine visualization tool that is used to explore and display search results from a standard search engine. This tool provides an alternate representation of the conventional search engines and allows three-dimensional navigation through the file system. This tool can be developed using Java2D and its three-dimensional extension API called Java 3D. The tool allows different customization options such as change the shape of objects in the world, and their colour. The design and implementation of the tool is discussed and further extensions are provided.
Domains	Web Application
Keywords	Java2D,Java 3D.
H/w & S/w	Java J2SE

ProjectName	Enforcing Minimum-Cost Multicast Routing against Selfish Information Flows
Abstract	We study multicast in a noncooperative environment where information flows selfishly route themselves through the cheapest paths available. The main challenge is to enforce such selfish multicast flows to stabilize at a socially optimal operating point incurring minimum total edge cost, through appropriate cost allocation and other economic measures, with replicable and encodable properties of information flows considered. We show that known cost allocation schemes are not sufficient. We provide a shadow-price-based cost allocation for networks without capacity limits and show that it enforces minimum-cost multicast. This improves previous result where a approximate multicast flow is enforced. For capacitated networks, computing cost allocation by ignoring edge capacities will not yield correct results. We show that an edge tax scheme can be combined with a cost allocation to strictly enforce optimal multicast flows in this more realistic case. If taxes are not desirable, they can be returned to flows while maintaining weak enforcement of the optimal flow. We relate the taxesto VCGpaymentschemesand discussan efficientprimal-dualalgorithmthatsimultaneously computesthe taxes,the cost allocation, and the optimal multicast flow, with potential of fully distributed implementations.
Domains	Parallel & Distributed Systems
Keywords	LP Formulations, Primal & Dual, Communication/networking, multicast, graph algorithms.
H/w & S/w	java with windows/Linux

ProjectName	Encrypted Voice Calls with IP enabled Wireless Phones over GSM/ CDMA/ WiFi Networks
Abstract	A research on the related technology and implementation of IP phone based on WiFi network is discussed in this paper; it includes the net structure of the technology used in designing the terminal of IP phone. This technology is a form of telecommunication that allows data and voice transmissions to be sent across a wide range of interconnected networks. A WiFi enabled IP phone is used which is preinstalled with the Symbian Operating System and a software application is developed using J2ME which allows free and secured communication between selected IP phones in the WiFi network. This communication is done with the use of routing tables organized in the WiFi routers. Using the free bandwidth of 2.4 GHz communication channels are established. The communication channel being a free bandwidth is vulnerable to external attacks and hacking. Thereby this challenge of creating a secure communication channel is addressed by using two different encryption mechanisms. The payload and header of the voice data packets encrypted using two different algorithm techniques. Hence the communication system is made almost fully secure. Also the WiFi server can tunnel the calls to the GSM network using UNC. Moreover the creation of a vertical handoff protocol will provide seamless communication for users. This handoff is defined in the context of a diverse network environment. It is cost effective, it allows easier communication, is great for international usages, and it can be very useful for large corporations. In time this will become a cheap and secure way to communicate and will have a large effect on university, business and personal communication.
Domains	Mobile Computing, Network Security.
Keywords	IP phones, Wifi ,Symbian, J2ME, encryption, GSM,UNC.
H/w & S/w	Java with windows/Linux

ProjectName	Remote Surveillance and Face Tracking with Mobile Phones (Smart Eyes)
Abstract	This thesis addresses analysis, evaluation and simulation of low complexity face detection algorithms and tracking that could be used on mobile phones. Network access control using face recognition increases the user-friendliness in human-computer interaction. In order to realize a real time system implemented on handheld devices with low computing power, low complexity algorithms for face detection and face tracking are implemented. Skin color detection algorithms and face matching have low implementation complexity suitable for authentication of cellular network services. Novel approaches for reducing the complexities of these algorithms and fast implementation are introduced in this thesis. This includes a fast algorithm for face detection in video sequences, using a skin color model in the HSV (Hue-Saturation-Value) color space. It is combined with a Gaussian model of the H and S statistics and adaptive thresholds. These algorithms permit segmentation and detection of multiple faces in thumbnail images. Furthermore we evaluate and compare our results with those of a method implemented in the Chromatic Color space (YCbCr). We also test our test data on face detection method using Convolutional Neural Network architecture to study the suitability of using other approaches besides skin color as the basic feature for face detection. Finally, face tracking is done in 2D color video streams using HSV as the histogram color space. The program is used to compute 3D trajectories for a remote surveillance system.
Domains	Mobile Computing, Intelligant Systems, J2ME.
Keywords	Remote Surveillance, Face Tracking, Mobile Phones, Face Detection, HSV Color Space, Face Recognition, Color Histogram, Skin Color Pixel, intensity gradient.
H/w & S/w	java with windows/Linux

ProjectName	Grid Banking System Structure
Abstract	Highly computational resource sharing environments like grids pose major security issues. Secure interoperability has been a growing concern for such multi domain computing systems. Collaboration in such a diverse environment requires integration of all local policies to compose a global access control policy for controlling information and resource. Access control in such an environment is still an open problem. The much standardized Role Based Access Control (RBAC) is yet to be fully utilized in a multi domain grid environment like the Grids. Here, we present an architectural framework for adaptation and implementation of RBAC for grid access control. Our approach includes solutions for delegation and revocation in a single domain grid enterprise like bank. The classical Role Based Access Control, though an effective access control standard, does not address the issue of resolving a local role into a global role. So, we also propose architecture based on RBAC, which can establish role equivalence among the domains by mapping a local domain role to its equivalent global role. We use the approach of weighted ranking for the same. The final authorization decision is made based on the mapped global role ranking. And also the resource access policies.
Domains	Grid Banking, Grid Computing.
Keywords	Role Based Access Control, Grid Banking, resource sharing, authorization policies.
H/w & S/w	java with windows 2000 onwards and Linux,SQL server 2000 onwards

ProjectName	A Role and Attribute Based Access Control System Using Semantic Web Technologies
Abstract	We show how Semantic Web technologies can be used to build an access control system. We follow the role-based access control approach (RBAC) and extend it with contextual attributes. Our approach provides for the dynamic association of roles with users. A Description Logic (DL) reasoner is used to classify both users and resources, and verify the consistency of the access control policies. We mitigate the limited expressive power of the DL formalism by refining the output of the DL reasoner with SPARQL queries. Finally, we provide a proof-ofconcept implementation of the system written in Java
Domains	Web Based Collaboration, Authorization Models
Keywords	RBAC (Role based access control), ABAC (Attribute Based access control),
H/w & S/w	Java, J2ME, windows/Linux

ProjectName	A Fully Automatic CAD-CTC System Based on Curvature Analysis for Standard and Low-Dose CT Data
Abstract	Computed tomography colonography (CTC) is a rapidly evolving noninvasive medical investigation that is viewed by radiologists as a potential screening technique for the detecby radiologists as a potential screening technique for the detection of colorectal polyps. Due to the technical advances in CT system design, the volume of data required to be processed by radiologists has increased significantly, and as a consequence the manual analysis of this information has become an increasingly time consuming process whose results can be affected by inter time consuming process whose results can be affected by interand intrauser variability. The aim of this paper is to detail the implementation of a fully integrated CAD-CTC system that is able to robustly identify the clinically significant polyps in the CT data.The CAD-CTC system described in this paper is a multistage implementation whose main system components are: 1) automatic colon segmentation; 2) candidate surface extraction; 3) feature extraction; and 4) classification. Our CAD-CTC system performs at 100% sensitivity for polyps larger than 10 mm, 92% sensitivity for polyps in the range 5 to 10 mm, and 57.14% sensitivity for polyps smaller than 5 mm with an average of 3.38 false positives per dataset. The developed system has been evaluated on synthetic and real patient CT data acquired with standard and low-dose radiation levels.
Domains	Image Processing.
Keywords	Classification, computed tomography (CT), convexity
H/w & S/w	java,windows/Linux

ProjectName	Patient Centric Medical Information System using Web Services
Abstract	This Software Requirements Specification provides a complete description of all the functions and specifications for the purpose of the project on Patient Centric Medical Information System Using Web Services. This Medical Information System deals with the Tuberculosis related data for the patients provided by means of Web Services. This system is beneficial for use mainly by the outdoor patients and medical professionals.
Domains	Web Services
Keywords	SOAP, WDSL, UML, BPEL.
H/w & S/w	Java,J2ME.windows/Linux

ProjectName	E-Learning as a Web Service
Abstract	E-learning has been a topic of increasing interest in recent years. It is often perceived as a group effort, where content authors, instructional designers, multimedia technicians, teachers, trainers, database administrators, and people from various other areas of expertise come together in order to serve a community of learners On the other hand, there are increasingly many activities which aim at providing services of any kind on the Web [9]; these can occur as business-tobusiness or as business-to-consumer services and are generally subsumed under the term Web services. In this paper we suggest to combine the areas of e-learning and Web services, by providing electronic learning offerings as (individual ) Web services as well. We elaborate on this by showing how content providers and content consumers (i.e., learners) can communicate appropriately through a Web service platform with its common description publication, and retrieval functionalities. Finally, we indicate how a corresponding system can be realized.
Domains	Web Services
Keywords	Learning Management System (LMS), LOM, SCORM, UDDI.
H/w & S/w	Java,J2ME.Windows/Linux

Java tutorials

2011-01-21T09:51:00.000-08:00

Click on below links to download

The Java SE Tutorials primarily describe features in Java SE 6. For best results, download JDK 6.

What's New

As part of the Oracle Author Podcast Series, a podcast on the Java Tutorials has just been released. You can hear the 10-minute podcast through the Oracle Author Podcasts website.

Enjoy quizzes? Take a minute to answer this quiz about Java applets.

The Java Tutorials are continuously updated to keep up with changes to the Java Platform and to incorporate feedback from our readers. Included in the most recent release:

For several months the Java SE Tutorials were not available as a download. We are happy to report that the very popular bundle is back and available through the link under the "Tutorial Resources" box to the right.
Do the Java Tutorials seem overwhelming to you? We have added a new Learning Paths page. Please let us know what you think!
The new Fork/Join page, part of the Concurrency lesson, describes how you can use the Fork/Join framework to take advantage of multiple processors. This feature is available now in the Java SE 7 release available on java.net.
The JDBC Basics lesson has been completely revamped, including updated sample code that you can download, compile, and run – the code has been configured for Java DB and MySQL. See Getting Started for more information.
Finally, a small, but notable, change is that the standalone JNDI tutorial, previously available on java.sun.com, has been moved to the Java SE documentation archive on download.oracle.com and many broken links in the tutorial have been fixed. The front page of the JNDI tutorial has been modified accordingly, and redirects are in place ensuring a seamless transition.

Trails Covering the Basics

These trails are available in book form as The Java Tutorial, Fourth Edition. To buy this book, refer to the box to the right.

Getting Started — An introduction to Java technology and lessons on installing Java development software and using it to create a simple program.
Learning the Java Language — Lessons describing the essential concepts and features of the Java Programming Language.
Essential Java Classes — Lessons on exceptions, basic input/output, concurrency, regular expressions, and the platform environment.
Collections — Lessons on using and extending the Java Collections Framework.
Swing — An introduction to the Swing GUI toolkit, with an overview of features and a visual catalog of components. See below for a more comprehensive tutorial on Swing.
Deployment — How to package applications and applets using JAR files, and deploy them using Java Web Start and Java Plug-in.
Preparation for Java Programming Language Certification — List of available training and tutorial resources.

Creating Graphical User Interfaces

This trail is available in book form as The JFC Swing Tutorial. To buy this book, refer to the box to the right.

Creating a GUI with Swing — A comprehensive introduction to GUI creation on the Java platform.

Specialized Trails and Lessons

These trails and lessons are only available as web pages.

Custom Networking — An introduction to the Java platform's powerful networking features.
The Extension Mechanism — How to make custom APIs available to all applications running on the Java platform.
Full-Screen Exclusive Mode API — How to write applications that more fully utilize the user's graphics hardware.
Generics — An enhancement to the type system that supports operations on objects of various types while providing compile-time type safety. Note that this lesson is for advanced users. The Java Language trail contains a Generics lesson that is suitable for beginners.
Internationalization — An introduction to designing software so that it can be easily be adapted (localized) to various languages and regions.
JavaBeans — The Java platform's component technology.
JDBC Database Access — Introduces an API for connectivity between the Java applications and a wide range of databases and a data sources.
JMX— Java Management Extensions provides a standard way of managing resources such as applications, devices, and services.
JNDI— Java Naming and Directory Interface enables accessing the Naming and Directory Service such as DNS and LDAP.
JAXP — Introduces the Java API for XML Processing (JAXP) 1.4 technology.
RMI — The Remote Method Invocation API allows an object to invoke methods of an object running on another Java Virtual Machine.
Reflection — An API that represents ("reflects") the classes, interfaces, and objects in the current Java Virtual Machine.
Security — Java platform features that help protect applications from malicious software.
Sound — An API for playing sound data from applications.
2D Graphics — How to display and print 2D graphics in applications.
Sockets Direct Protocol — How to enable the Sockets Direct Protocol to take advantage of InfiniBand.

Computers and Programming

2011-01-14T01:40:00.001-08:00

Hardware and Software

A computer is a device capable of performing computations and making logical decisions at speeds millions and even billions of times faster than human beings can. For example, many of today’s personal computers can perform hundreds of millions of additions per second.

Computers process data under the control of sets of instructions called computer programs. These computer programs guide the computer through orderly sets of actions specified by people called computer programmers.

A computer is comprised of various devices (such as the keyboard, screen, “mouse”, disks, memory, CD-ROM and processing units) that are referred to as hardware. The computer programs that run on a computer are referred to as software.

Computer Hardware

Almost every computer may be seen as being divided into six logical units. Figure 1 illustrates the main computer components.

Input Unit

This unit obtains information from various input devices and places this information at the disposal of the other units so that the information may be processed. The information is entered into computers today through keyboards and mouse devices.

Output Unit

This unit takes information that has been processed by the computer and places it on various output devices to make information available for use outside the computer. Most output from computer today is displayed on screens, printed on paper, or used to control other devices.

Memory Unit

The memory unit stores information. Each computer contains memory of two main types: RAM and ROM.

RAM (random access memory) is volatile. Your program and data are stored in RAM when you are using the computer.

**Figure 1:** Basic hardware units of a computer

ROM (read only memory) contains fundamental instructions that cannot be lost or changed by the user. ROM is non-volatile.

Arithmetic and Logic Unit (ALU)

The ALU performs all the arithmetic and logic operations. Ex: addition, subtraction, comparison, etc.

Central Processing Unit (CPU)

The unit supervises the overall operation of the computer. The CPU tells the input unit when information should be read into the memory unit, tell the ALU when information from the memory should be used in calculations and tells the output unit when to send information from the memory unit to certain output devices.

Secondary Storage

Secondary storage devices are used to be permanent storage area for programs and data.

Virtually all secondary storage is now done on magnetic tapes, magnetic disks and CD-ROMs.

A magnetic hard disk consists of either a single rigid platter or several platters that spin together on a common spindle. A movable access arm positions the read and write mechanisms over, but not quite touching, the recordable surfaces. Such a configuration is shown in Figure 2.

**Figure 2:** The internal structure of a magnetic hard disk drive

Computer Software

A computer program is a set of instructions used to operate a computer to produce a specific result.

Another term for a program or a set of programs is software, and we use both terms interchangeably throughout the text.

Writing computer programs is called computer programming.

The languages used to create computer programs are called programming languages.

To understand C++ programming, it is helpful to know a little background about how current programming languages evolved.

Machine and Assembly Languages

Machine languages are the lowest level of computer languages. Programs written in machine language consist of entirely of 1s and 0s.

Programs in machine language can control directly to the computer’s hardware.

00101010 000000000001 000000000010

10011001 000000000010 000000000011

A machine language instruction consists of two parts: an instruction part and an address part.

The instruction part (opcode) is the leftmost group of bits in the instruction and tells the computer the operation to be performed.

The address part specifies the memory address of the data to be used in the instruction.

Assembly languages perform the same tasks as machine languages, but use symbolic names for opcodes and operands instead of 1s and 0s.

LOAD BASEPAY

ADD OVERPAY

STORE GROSSPAY

Since computers can only execute machine language programs, an assembly language program must be translated into a machine language program before it can be executed on a computer.

**Figure 3:** Assembly translation

Machine languages and assembly languages are called low-level languages since they are closest to computer hardware.

High-level Programming Languages

High-level programming languages create computer programs using instructions that much easier to understand than machine or assembly language instructions.

Programs written in a high-level language must be translated into a low level language using a program called a compiler.

A compiler translates programming code into a low-level format.

High-level languages allow programmers to write instructions that look like every English sentences and commonly used mathematical notations.

Each line in a high-level language program is called a statement.

Ex: Result = (First + Second)*Third.

Once a program is written in a high-level language, it must also be translated into the machine language of the computer on which it will be run. This translation can be accomplished in two ways.

When each statement in a high-level source program is translated individually and executed immediately upon translation, the programming language used is called an interpreted language, and the program doing the translation is called an interpreter.

When all of the statements in a high-level source program are translated as a complete unit before any one statement is executed, the programming language used is called is called a compiled language. In this case, the program doing the translation is called a compiler.

Application and System Software

Two types of computer programs are: application software and system software.

Application software consists of those programs written to perform particular tasks required by the users.

System software is the collection of programs that must be available to any computer system for it to operate.

The most important system software is the operating system. Examples of some well-known operating systems include MS-DOS, UNIX, and MS WINDOWS. Many operating systems allow user to run multiple programs. Such operating systems are called multitasking systems.

Beside operating systems, language translators are also system softwares.

High-Level Programming Languages

Because of the difficulty of working with low-level languages, high-level languages were developed to make it easier to write computer programs. High level programming languages create computer programs using instructions that are much easier to understand than machine or assembly language code because you can use words that more clearly describe the task being performed. Examples of high-level languages include FORTRAN, COBOL, BASIC, PASCAL, C, C++ and JAVA.

C and C++ are two separate, but related programming languages. In the 1970s, at Bell Laboratories, Dennis Ritchie and Brian Kernighan designed the C programming language. In 1985, at Bell Laboratories, Bjarne Stroutrup created C++ based on the C language. C++ is an extension of C that adds object-oriented programming capabilities.

What is Syntax?

A programming language’s syntax is the set of rules for writing grammatically correct language statements. In practice this means a C statement with correct syntax has a proper form specified for the compiler. As such, the compiler accepts the statement and does not generate an error message.

The C Programming Language

C was used exclusively on UNIX and on mini-computers. During the 1980s, C compilers were written for other platforms, including PCs.

To provide a level of standardization for C language, in 1989, ANSI created a standard version of C that is called ANSI C.

One main benefit of the C language is that it is much closer to assembly language other than other types of high-level programming languages.

The programs written in C often run much faster and more efficiently than programs written in other types of high-level programming language.

The C++ Programming Language

C++ is an extension of C that adds object-oriented programming capabilities. C++ is a popular programming language for writing graphical programs that run on Windows and Macintosh.

The standardized version of C++ is commonly referred to as ANSI C++.

The ANSI C and ANSI C++ standards define how C/C++ code can be written.

The ANSI standards also define run-time libraries, which contains useful functions, variables, constants, and other programming items that you can add to your programs.

The ANSI C++ run-time library is also called the Standard Template Library or Standard C++ Library.

Structured Programming and Object Oriented Programming

During the 1960s, many large software development effects encountered severe difficulties. Software schedules were typically late, costs greatly exceeded budgets and finished products were unreliable. People began to realize that software development was a far more complex activity than they had imagined. Research activity in the 1960s resulted in the evolution of structured programming – a discipline approach to writing programs that are clearer than unstructured programs, easier to test and debug and easier to modify. Chapter 5 discusses the principles of structured programming. Chapters 2 through 6 develop many structured programs.

One of the more tangible results of this research was the development of the Pascal programming language by Niklaus Wirth in 1971. Pascal was designed for teaching structured programming in academic environments and rapidly became the preferred programming languages in most universities.

In the 1980s, there is a revolution brewing in the software community: object- oriented programming. Objects are essentially reusable software components that model items in the real world. Software developers are discovering that using a modular, object-oriented design and implementation approach can make software development groups much more productive than with previous popular programming techniques such as structured programming.

Object-oriented programming refers to the creation of reusable software objects that can be easily incorporated into another program. An object is programming code and data that can be treated as an individual unit or component. Data refers to information contained within variables, constants, or other types of storage structures. The procedures associated with an object are referred as functions or methods. Variables that are associated with an object are referred to as properties or attributes. Object-oriented programming allows programmers to use programming objects that they have written themselves or that have been written by others.

Problem Solution and Software Development

No matter what field of work you choose, you may have to solve problems. Many of these can be solved quickly and easily. Still others require considerable planning and forethought if the solution is to be appropriate and efficient.

Creating a program is no different because a program is a solution developed to solve a particular problem. As such, writing a program is almost the last step in a process of first determining what the problem is and the method that will be used to solve the problem.

One technique used by professional software developers for understanding the problem that is being solved and for creating an effective and appropriate software solution is called the software development procedure. The procedure consists of three overlapping phases

- Development and Design

- Documentation

- Maintenance

As a discipline, software engineering is concerned with creating readable, efficient, reliable, and maintainable programs and systems.

Phase I: Development and Design

The first phase consists of four steps:

1. Analyze the problem

This step is required to ensure that the problem is clearly defined and understood. The person doing the analysis has to analyze the problem requirements in order to understand what the program must do, what outputs are required and what inputs are needed. Understanding the problem is very important. Do not start to solve the problem until you have understood clearly the problem.

2. Develop a Solution

Programming is all about solving problems. In this step,

you have to develop an algorithm to solve a given problem. Algorithm is a sequence of steps that describes how the data are to be processed to produce the desired outputs.

An algorithm should be (at least)

–complete (i.e. cover all the parts)

–unambiguous (no doubt about what it does)

–finite (it should finish)

3. Code the solution

This step consists of translating the algorithm into a computer program using a programming language.

4. Test and correct the program

This step requires testing of the completed computer program to ensure that it does, in fact, provide a solution to the problem. Any errors that are found during the tests must be corrected.

Figure below lists the relative amount of effort that is typically expended on each of these four development and design steps in large commercial programming projects.

**Figure 4:** Four development and design steps in commercial programming projects

Phase II: Documentation

Documentation requires collecting critical documents during the analysis, design, coding, and testing.

There are five documents for every program solution:

Program description
Algorithm development and changes
Well-commented program listing
Sample test runs
User’s manual

Phase III: Maintenance

This phase is concerned with the ongoing correction of problems, revisions to meet changing needs and the addition of new features. Maintenance is often the major effort, and the longest lasting of the three phases. While development may take days or months, maintenance may continue for years or decades.

Algorithms

An algorithm is defined as a step-by-step sequence of instructions that describes how the data are to be processed to produce the desired outputs. In essence, an algorithm answers the question: “What method will you use to solve the problem?”

You can describe an algorithm by using flowchart symbols. By that way, you obtain a flowchart which is an outline of the basic structure or logic of the program.

Flowchart Symbols

To draw flowchart, we employ the symbols shown in the Figure below.

**Figure 5:** Flowchart symbols

The meaning of each flowchart symbol is given as follows.

**Figure 6:** Description of flowchart symbols

To illustrate an algorithm, we consider the simple program that computes the pay of a person. The flowchart for this program is given in the Figure below.

Note: Name, Hours and Pay are variables in the program.

**Figure 7:** A sample flowchart

Algorithms in pseudo-code

You also can use English-like phases to describe an algorithm. In this case, the description is called pseudocode. Pseudocode is an artificial and informal language that helps programmers develop algorithms. Pseudocode has some ways to represent sequence, decision and repetition in algorithms. A carefully prepared pseudocode can be converted easily to a corresponding C++ program.

Example: The following set of instructions forms a detailed algorithm in pseudocode for calculating the payment of person.

Input the three values into the variables Name, Hours, Rate.

Calculate Pay = Hours  Rate.

Display Name and Pay.

Loops in Algorithms

Many problems require repetition capability, in which the same calculation or sequence of instructions is repeated, over and over, using different sets of data.

Example 1.1. Write a program to do the task: Print a list of the numbers from 4 to 9, next to each number, print the square of the number.

The flowchart for the algorithm that solves this problem is given in Figure below. You will see in this figure the flowchart symbol for decision and the flowline that can connect backward to represent a loop.

**Figure 8:** Flowcharts of example 1.1

Note:

In the flowchart, the statement

NUM = NUM + 1

means “old value of NUM + 1 becomes new value of NUM ”.

The above algorithm can be described in pseudocode as follows:

NUM = 4

do

SQNUM = NUM*NUM

Print NUM, SQNUM

NUM = NUM + 1

while (NUM <= 9)

You can compare the pseudo-code and the flowchart in Figure above to understand the meaning of the do… while construct used in the pseudo-code.

Flowchart versus pseudocode

Since flowcharts are inconvenient to revise, they have fallen out of favor by programmers. Nowadays, the use of pseudocode has gained increasing acceptance.

Only after an algorithm has been selected and the programmer understands the steps required can the algorithm be written using computer-language statements. The writing of an algorithm using computer-language statements is called coding the algorithm, which is the third step in our program development process.

Parallel Programming with MapReduce

2011-01-14T01:39:00.001-08:00

MapReduce Overview

MapReduce is a framework designed by Google [1]. It is loosely based on the Map and Reduce programming constructs of functional languages like Lisp [2]. Google’s MapReduce is used in a distributed computing, scalable platform. It was designed for data-intensive applications which need to process huge amounts of data.

Various open source implementations exist. The most popular one is Apache’s Hadoop [3]. Hadoop is a scalable distributed computing platform that includes a file system (HDFS) to store massive data, and a Java MapReduce implementation to process that data.

Other MapReduce implementations exist. QT Concurrent has a MapReduce implementation for multi-core processors.

This module provides an introduction to parallel programming with MapReduce, using QT Concurrent.

Programming with MapReduce

When we decide to solve a programming problem using MapReduce, we provide an implementation for a mapper and for a reducer. N mappers are executed simultaneously, executing the same task for different input data. One or more reducers receive the output generated by the mappers, and apply a reducing phase yielding a final result.

A simple program to count word occurrences in a text corpus is described in [4]:


   map(String input_key, String input_value):
       // input_key: document name 
       // input_value: document contents 
       for each word w in input_value: 
           EmitIntermediate(w, "1"); 

    reduce(String output_key, Iterator intermediate_values): 
       // output_key: a word 
       // output_values: a list of counts 
       int result = 0; 
    
       for each v in intermediate_values: 
          result += ParseInt(v);
       Emit(AsString(result));

MapReduce pseudocode that counts word occurrences in a text corpus.

As shown in the code above, a map function receives an input key and an input value (<key, value>), and generates one or more intermediate output <key,value(s)> pairs. A reduce function receives intermediate keys and values that were the ouput by the mappers, processes them in some way, and generates one or more final key-value(s) pairs (<key,value(s)).

You can find a Hadoop implementation of the word count problem at [5], and a QT concurrent implementation in the QT Concurrent package (path: qtconcurrent/examples/wordcount) which can be checked out with subversion.

MapReduce in QT Concurrent

QT Concurrent [6] is a C++ library for multi-threaded applications. Among other things, it provides a MapReduce implementation for multi-core computers. The map function is called in parallel by multiple threads. The number of threads used in a program depends on the number of processor cores available.

Google’s original MapReduce runs in computer clusters. The data it processes is stored in a distributed file system called GFS (Google File System). To minimize I/O bottlenecks, mappers are usually executed in the same node where the data resides. Parallelism comes from multiple computers executing mappers (or reducers) at the same time.

On the other hand, QT Concurrent’s MapReduce implementation works on shared-memory systems. Parallelism comes from multiple threads executing mappers at the same time, on multiple processor cores.

To work with QT Concurrent’s MapReduce, you write a map function and a reduce function. You must also indicate the list of values (e.g., names of files, words, numbers, etc.) that you want to feed your mappers. To do this, use the following API:


QFuture<T> QtConcurrent::mappedReduced ( 
    const Sequence & sequence, 
    MapFunction mapFunction, 
    ReduceFunction reduceFunction, 
    QtConcurrent::ReduceOptions reduceOptions = UnorderedReduce | SequentialReduce )

Structure QTConcurrent::mappedReduced function

For example:


QFuture<T> mappedReduced(theList, mapFunction, reduceFunction);

QFuture::mappedReduced function

Example: Determining if a (Big) Integer is a Probable Prime

An algorithm for finding a probable prime can be defined using the Miller-Rabin primality test, as follows:

    
    let n be a very big odd number
    check n for divisibility for all primes < 2000
    choose m positive integers less than n
    for each of these bases apply the Miller-Rabin test

The algorithm described above can be easily parallelized using MapReduce as follows:

Step 1. Randomly generate an odd (big) integer n greater than 2.
Step 2. Generate (or read a list of) all primes less than 2000.
Step 3. MapReduce-Part1:
- Map function: Each mapper receives a distinct prime number p_i, and checks if n is divisible by this number. A mapper emits (outputs) a 1 if n is divisible by p_i or 0 otherwise.
- Reduce function: Counts the number of divisors. If the number of divisors is greater than zero, it is not a prime number, so the test is terminated.
Step 4. Generate 100 random positive integers less than n.
Step 5. MapReduce-Part2:
- Map function: Each mapper receives a different random number r_i and applies the Miller-Rabin primality test. A mapper emits (outputs) a 1 if n does not pass the test, or a 0 if it passes the test.
- Reduce function: Counts the number of 1s emitted by the mappers. If the number of divisors is zero, n is a probable prime.

The next section shows a MapReduce implementation of the algorithm described above, using QT Concurrent. You can find a Hadoop implementation here.

A MapReduce Implementation Using QT Concurrent

The main program needs to call the mappedReduced function twice (steps 3 and 5 in the algorithm described earlier):


    qDebug() << "\nJob: Divisibility for primes less than 2000";
    qDebug() << "Starting Job";
    
    time.start();
    Counting final = mappedReduced(primes,mapperLess2000,reducerLess2000);
    mapReduce2000Time = time.elapsed();
    qDebug() << "End Job";
    qDebug() << "MapReduce elapsed time: " << (mapReduce2000Time) << "msegs\n";
    
    //Counter of exacts divisors equals to zero
    if(final[exactDiv] == 0) {

       de = Decomposition<2048>(number - 1);

       qDebug() << "Job: Divisibility for random numbers less than number to evaluate";
       qDebug() << "Starting Job";
       time.start();
       Counting finalRand = mappedReduced(randomPrimes,mapperRandom,reducerRandom);
       mapReduceRandomTime = time.elapsed();
       qDebug() << "End Job";
       qDebug() << "MapReduce elapsed time: " << (mapReduceRandomTime) << "msegs\n";
    
       //Counter of random numbers
       if(finalRand[falseMiller] > 0) {
          qDebug() << "Result: Non-prime";
       } else
          qDebug() << "Result: Probably prime";
    } else qDebug() << "Result: Non-prime";

Main program

The Decomposition function used in the main program because number decomposition is needed before the Miller-Rabin test is performed. This means that the number minus one is represented as product of 2^k and m, where m is odd.

Two MapReduce processes are implemented. The first MapReduce process, evaluates divisibility for all primes less than 2000. Each map function receives a prime as argument and the reduce function counts the number of divisors, as shown below:


    Counting mapperLess2000(const unsigned long &prime) {
       Counting rMap; 
       BigInt2048 myPrime(prime);
    
       if( number % myPrime == 0 )
          divisors << prime; 
    
       rMap[( number % myPrime == 0 )?exactDiv:inexactDiv];
       return rMap;
    }
    
    void reducerLess2000(Counting &result, const Counting &w) {
        QMapIterator<QString, int> i(w); 
    
        while(i.hasNext()) {
           i.next();
           result[i.key()]++;
        }
    }

MapReduce code to test for primality

The second MapReduce process is executed only if the random number was not divisible by any of the prime numbers less than 2000:


    Counting mapperRandom(const BigInt2048 &prime) {
        
        Counting rMap;
        BigInt2048 z( getZ(prime,de.getM()).bits );
    
        // This is the easy case; the first term in the sequence
        // is correct, so we pass the test.
    
        if(z == 1) {

           rMap[trueMiller];
           divisors << z;
           return rMap;

        } else {
    
           for (int j = 0; j < de.getK(); j++) {
               BigInt2048 zSquared = BigInt2048(newZ(z).bits);
           
               if (zSquared == 1 && z == (number - 1) ) {
    
                  // We've passed the hard version of the Rabin Miller test.
                  rMap[trueMiller];
                  divisors << z;
                  return rMap;

               }
           
               z = zSquared;
           }
        
           rMap[falseMiller];
           return rMap;
        }
    }
    
    
    void reducerRandom(Counting &result, const Counting &w) {

        QMapIterator<QString, int> i(w);
        while(i.hasNext()) {
            i.next();
            result[i.key()]++;
        }
    }

MapReduce code that applies the Miller-Rabin test

Figure 1 shows the results of one run of the program.

**Figure 1:** Prime Validator program

You can download the complete source of this example here.

References

[1] Jeffrey Dean, Sanjay Ghemawat. “MapReduce: Simplified Data Processing on Large Clusters.” In Communications of the ACM, vol. 51, no. 1 (2008). pp. 107-113.
[2] McCarthy, J. "Recursive functions of symbolic expressions and their computation by machine, Part I". In Communications of the ACM. Vol 3 (4), pp. 184-195. Apr. 1960. http://www-formal.stanford.edu/jmc/recursive.pdf
[3] Apache Hadoop, http://hadoop.apache.org/, 03/17/2009
[4] Aaron Kimball, Sierra Michels-Slettvet, Christophe Bisciglia, et al. , “Lecture 2 - MapReduce: Theory and Implementation”. Introduction to Problem Solving on Large Scale Clusters. Spring 2007. Available for download at: http://code.google.com/edu/submissions/uwspr2007_clustercourse/listing.html
[5] Hadoop Wiki WordCount, http://wiki.apache.org/hadoop/WordCount, 24/09/2008
[6] Qt Concurrent, http://labs.trolltech.com/page/Projects/Threads/QtConcurrent , 12/02/2008

Decorator Design Pattern

2011-01-14T01:30:00.001-08:00

The Decorator Pattern is used for adding additional functionality to a particular object as opposed to a class of objects. It is easy to add functionality to an entire class of objects by subclassing an object, but it is impossible to extend a single object this way. With the Decorator Pattern, you can add functionality to a single object and leave others like it unmodified.

A Decorator, also known as a Wrapper, is an object that has an interface identical to an object that it contains. Any calls that the decorator gets, it relays to the object that it contains, and adds its own functionality along the way, either before or after the call. This gives you a lot of flexibility, since you can change what the decorator does at runtime, as opposed to having the change be static and determined at compile time by subclassing. Since a Decorator complies with the interface that the object that it contains, the Decorator is indistinguishable from the object that it contains. That is, a Decorator is a concrete instance of the abstract class, and thus is indistinguishable from any other concrete instance, including other decorators. This can be used to great advantage, as you can recursively nest decorators without any other objects being able to tell the difference, allowing a near infinite amount of customization.

**Figure 1:** Decorator example showing two concrete decorators that add additional state and behavior respectively.
UML diagram of a decorator design pattern example

Decorators add the ability to dynamically alter the behavior of an object because a decorator can be added or removed from an object without the client realizing that anything changed. It is a good idea to use a Decorator in a situation where you want to change the behaviour of an object repeatedly (by adding and subtracting functionality) during runtime. The dynamic behavior modification capability also means that decorators are useful for adapting objects to new situations without re-writing the original object's code. The code for a decorator would something like this:

void doStuff() {
   // any pre-processing code goes here.
   aComponent.doStuff();  // delegate to the decoree 
   // any post-processing code goes here
}

Note that the decorator can opt to not delegate to the decoree, if, for instance, some condition was not met. A very nice example of decorators is Java's I/O stream implementation.

This module is based on work originally written by Antonio Garcia

Data with phonetic characters using Easy IPA

2011-01-14T01:27:00.003-08:00

Summary: The whole IPA alphabet, including diacritics and modifiers, is available to you through Easy IPA. If you touch type, you'll find yourself touch typing the IPA characters you use frequently in your collection.

You can type anything the International Phonetic Alphabet offers without having to lift your hands from the keyboard. Here's how Easy IPA works:

Type the character from a to z that looks most like the character you want.
Type Control-space by putting your little finger on the Control key, and while holding it down, tap the space bar once with your index finger.
Look at the popup box that contains all the IPA characters that are kind of like the one you typed in Step 1.
Choose the IPA character you want.
Type the number or letter associated with it.
The IPA character replaces the a to z character you typed.

That's Easy IPA in a nutshell. Say you type an "a" to get an a-like vowel symbol such as ash (also called digraph). Then you type Control-space. Up come all the a-like characters:

**Figure 1:** Characters kind of like a in Wordcorr's Easy IPA table.

Ash is indexed as "2", so you type 2. It replaces the "a" you typed before the Control-space. If you wanted "a-breve" (not an IPA symbol, but comparative linguists use it anyway so we stuck it in the table) you'd type "c" to select it.

For IPA modifiers and some other characters, you type certain characters outside the a-z range before you type Control-space:

Glottal stop and similar characters: type "?" and Control-space.
Symbols for clicks: type "!" and Control-space.
Modifier characters: type "^" (Shift-6) and Control-space for some, ":" (colon) and Control-space for others.
Prosodic modifier characters: type ":" (colon) and Control-space.

For IPA diacritics that go under, above or through the base character proper:

Diacritics that mainly go under the base character, type "," (comma) and Control-space.
Diacritics that go above the base character, type "~" (tilde) and Control-space.
Diacritics that mainly go through the base character, type "-" (tilde) and Control-space.

Or, on a single line: Ctrl-Sp after ? glottal; ! click; ^ : modifier; , ~ - diacritic

**Figure 2:** IPA transcriptions from the Wordcorr Data panel. Diacritical marks are not well aligned here, but they are elsewhere.

HINT:

When you're typing in data, you don't use all the characters in the International Phonetic Alphabet. For the ones you use a lot, your brain quickly learns the motor sequence (like "a" Control-space "2" for ash). If you touch type, you'll soon find yourself touch typing the part of IPA you use without a blink. You don't even have to take your hands off the keyboard to look for a mouse or a reference card. Install Wordcorr and give it a try.

Drag and Drop Basics

2011-01-14T01:27:00.001-08:00

I recommend that you open another copy of this document in a separate browser window and use the following links to easily find and view the figures and listings while you are reading about them.

Figures

Figure 1 . Program output at startup.
Figure 2 . Program file structure.
Figure 3 . Program output after dragging the images.

Listings

Listing 1 . The MXML file for DragAndDrop01.
Listing 2 . Beginning of the Driver class for DragAndDrop01.
Listing 3 . Beginning of the constructor for the Driver class.
Listing 4 . Prepare the three images.
Listing 5 . Register a creationComplete event handler.
Listing 6 . Beginning of the creationComplete event handler.
Listing 7 . Register a mouseDown event handler on each Image object.
Listing 8 . Register dragDrop and dragEnter event handlers on the Canvas object.
Listing 9 . Beginning of the mouseDown event handler.
Listing 10 . Get and save the drag initiator.
Listing 11 . Populate a DragSource object with a copy of the image being dragged.
Listing 12 . Initiate the drag and drop operation by calling the doDrag method.
Listing 13 . The dragEnter event handler.
Listing 14 . Beginning of the dragDrop event handler.
Listing 15 . Do the drop.
Listing 16 . The MXML file for DragAndDrop01.
Listing 17 . The ActionScript file for DragAndDrop01.

Supplemental material

I recommend that you also study the other lessons in my extensive collection of online programming tutorials. You will find a consolidated index at www.DickBaldwin.com .

General Background Information

For Adobe online documentation on this topic, see Using Drag and Drop .

A drag and drop operation is carried out in three stages:

Initiation
Dragging
Dropping

Initiation

As you are probably already aware, initiation consists of the user pointing to an item with the mouse and pressing the mouse button.

Dragging

During the drag operation, the user drags the item to another location on the screen without releasing the mouse button.

Dropping

When the item has been dragged to the new location, the user releases the mouse button causing the item to remain in the new location.

Copying

It is also possible to copy an item using the drag and drop gestures, but that capability won't be illustrated in this lesson. Instead, this lesson will concentrate on moving a Flex component from one location in its container to a different location in its container.

Classes and events

The sample program that I will explain in this lesson will use the following classes, methods, and events:

MouseEvent class
- mouseDown event
DragEvent class
- dragDrop event
- dragEnter event
DragManager class
- acceptDragDrop method
- doDrag method
DragSource class
- addData method
- hasFormat method

Preview

I will explain a program named DragAndDrop01 . This program illustrates the fundamentals of drag and drop in ActionScript 3. The program places three images in the upper-left corner of aCanvas object as shown in Figure 1.

**Figure 1:** Program output at startup.
Program output at startup.

The program file structure

The program file structure, taken from the Flex Builder 3 Navigator panel is as shown in Figure 2.

**Figure 2:** Program file structure.
Program file structure.

Three image files

As you can see in Figure 2, the program uses the following image files :

0 - space.jpg
1 - snowscene.jpg
2 - frog.jpg

The z-axes indices

The program sets the z-axis indices in the order shown in the above list on the Image objects produced using the image files. This causes the space image to be in the back (0), the frogimage to be in the front (2), and the snowscene image to be in the middle (1).

The three images are initially placed in the upper-left corner of the canvas, which is shown as a cyan rectangle in Figure 1.

Any image can be dragged

If you run this program, you will see that any any of the images can be dragged and dropped anywhere within the canvas as long as the mouse pointer doesn't leave the canvas. However, if the edge of the dragged image goes outside the left edge or the top of the canvas, the drag and drop operation is aborted.

If the dragged image goes outside the right side or the bottom of the canvas, scroll bars automatically appear on the canvas as shown in Figure 3.

Program output after dragging the images

Figure 3 shows the program output after dragging the three images to different locations.

**Figure 3:** Program output after dragging the images.
Program output after dragging the images.

Discussion and sample code

Will explain in fragments

I will explain the code for this program in fragments. Complete listings of the MXML code and the ActionScript code are provided in Listing 16 and Listing 17 near the end of the lesson.

The MXML file

The MXML file is shown in Listing 1 and also in Listing 16 for your convenience.

LISTING 1: he MXML file for DragAndDrop01.

<?xml version="1.0" encoding="utf-8"?>
<!--DragAndDrop01-->

<mx:Application 
  xmlns:mx="http://www.adobe.com/2006/mxml" 
  xmlns:cc="CustomClasses.*">
  
  <cc:Driver/>

</mx:Application>

As you can see, the MXML file is very simple because the program was coded almost entirely in ActionScript. The MXML code simply instantiates an object of the Driver class. From that point forward, the behavior of the program is controlled by ActionScript code.

The ActionScript file

Beginning of the Driver class

The Driver class begins in Listing 2.

LISTING 2: Beginning of the Driver class for DragAndDrop01.

package CustomClasses{
  import flash.events.MouseEvent;
  
  import mx.containers.Canvas;
  import mx.controls.Image;
  import mx.core.DragSource;
  import mx.events.DragEvent;
  import mx.events.FlexEvent;
  import mx.managers.DragManager;

  //====================================================//
  
  public class Driver extends Canvas {
    private var imageA:Image = new Image();
    private var imageB:Image = new Image();
    private var imageC:Image = new Image();
    private var localX:Number;
    private var localY:Number;

Extends the Canvas class

As you can see in Listing 2, the Driver class extends the Canvas class. Therefore, an object of the Driver class is a Canvas object and has all of the attributes associated with a Canvasobject. Among those attributes is the following, which was taken from the documentation :

"A Canvas layout container defines a rectangular region in which you place child containers and controls. It is the only container that lets you explicitly specify the location of its children within the container by using the x and y properties of each child."

As you will see, the new location of each image is explicitly specified each time it is dragged to a new location.

Instantiate three new Image objects

The code in Listing 2 instantiates three new Image objects, which will be loaded with the contents of the three image files listed earlier . The code in Listing 2 also declares two instance variables that will be used to store the position of the mouse pointer within an image when the drag operation is initiated.

Beginning of the constructor for the Driver class

The constructor for the Driver class begins in Listing 3.

LISTING 3: Beginning of the constructor for the Driver class.

    public function Driver(){//constructor
      setStyle("backgroundColor",0x00FFFF);
      setStyle("backgroundAlpha",1.0);

Make the canvas visible

Normally a Canvas object is not visible. The code in Listing 3 sets the alpha value for the Canvas object to 1.0 making it opaque and visible. Listing 3 also sets the background color of the Canvas object to cyan as shown in Figure 1.

The size of the Canvas object will be set later when the Canvas object and all of its children have been constructed.

Prepare the three images

Listing 4 prepares the three images for use by the program.

LISTING 4: Prepare the three images.

      //Embed the image files in the SWF file.
      [Embed("snowscene.jpg")]
      var imgA:Class;
      
      [Embed("space.jpg")]
      var imgB:Class;
      
      [Embed("frog.jpg")]
      var imgC:Class;
      
      //Load the images from the embedded image files
      // into the Image objects.
      imageA.load(imgA);
      imageB.load(imgB);
      imageC.load(imgC);
      
      // Set the z-axes indices such that the frog is
      // in front, the snowscene is in the middle and the 
      // space image is at the back.
      addChildAt(imageB,0);//set index to 0
      addChildAt(imageA,1);//set index to 1
      addChildAt(imageC,2);//set index to 2

Listing 4 begins by embedding the three image files in the SWF file. Then it loads the contents of the image files into the Image objects instantiated in Listing 2. Finally Listing 3 adds the Image objects as children of the Canvas object.

Set the z-axis indices

The z-axis index of each Image object is set in Figure 4 so as to place the space image at the back, the frog image at the front, and the snowscene image between the other two.

Register a creationComplete event handler

Listing 5 registers a creationComplete event handler on the Canvas object. This event handler will be executed after the Canvas object and all of its children are fully constructed.

LISTING 5: Register a creationComplete event handler.

      this.addEventListener(FlexEvent.CREATION_COMPLETE,
                                         completeHandler);
    } //end constructor

Beginning of the creationComplete event handler

The creationComplete event handler begins in Listing 6. This handler is executed once when the Canvas object and all of its children have been constructed.

LISTING 6: Beginning of the creationComplete event handler.

    private function completeHandler(
                          event:mx.events.FlexEvent):void{
      //Set the width and height of the canvas based on 
      // the dimensions of imageB.
      this.width = 1.3*imageB.width;
      this.height = 1.3*imageB.height;

Set the size of the Canvas object

Listing 6 sets the width and height of the Canvas object based on the dimensions of the Image object referred to by imageB . It was not possible to reliably execute this code in the constructor because the code might be executed before the contents of the image file were fully loaded into the Image object.

Register a mouseDown event handler on each Image object

A drag and drop operation is heavily dependent on the handling of different types of events. The remaining code in the creationComplete event handler registers appropriate event handlers on the images and on the Canvas object to support the drag and drop operation with the Canvas object as the drag target.

As you will see later, a drag operation is initialized when an image dispatches a mouseDown event. Listing 7 registers the same mouseDown event handler on all three Image objects.

LISTING 7: Register a mouseDown event handler on each Image object.

      imageA.addEventListener(MouseEvent.MOUSE_DOWN,
                                        mouseDownHandler);
      imageB.addEventListener(MouseEvent.MOUSE_DOWN,
                                        mouseDownHandler);
      imageC.addEventListener(MouseEvent.MOUSE_DOWN,
                                        mouseDownHandler);

Register dragDrop and dragEnter event handlers on the Canvas object

Two different event handlers must be registered on the drag target, which is the Canvas object in this case. The registration of those event handlers on the Canvas object is accomplished in Listing 8.

LISTING 8: Register dragDrop and dragEnter event handlers on the Canvas object.

      this.addEventListener(DragEvent.DRAG_DROP,
                                             dropHandler);
      this.addEventListener(DragEvent.DRAG_ENTER,
                                        enterHandler);
    } //end completeHandler

Beginning of the mouseDown event handler

The mouseDown event handler that was registered on the Image objects in Listing 7 begins in Listing 9. This event handler initiates the drag and drop operation on the Image object that dispatches the event.

LISTING 9: Beginning of the mouseDown event handler.

    private function mouseDownHandler(
                                   event:MouseEvent):void{

      //Save the location of the mouse within the image
      // being dragged. This information will be used
      // later to properly position the dropped image in
      // the drop target.
      this.localX = event.localX;
      this.localY = event.localY;

Positioning the dropped object

The easiest approach simply drops the image with its upper-left corner at the position of the mouse pointer when the mouse button is released. However, in my opinion, that is somewhat less than satisfactory from a visual viewpoint.

The drag proxy

When you drag an image, there is a default drag proxy that moves along with the mouse. (It is possible to replace the default drag proxy with a drag proxy of your choice.) The default drag proxy is a partially transparent rectangle that is the same size as the image.

Adjust the position of the upper-left corner

My preference is to manually adjust the drop location of the image based on the upper-left corner of the drag proxy and not based on the location of the mouse pointer. The code in Listing 9 gets and saves the coordinates of the mouse pointer within the image when the event is dispatched. As you will see later, I use these coordinates later to set the drop location on the basis of the upper-left corner of the proxy.

Get and save the drag initiator

The documentation refers to the object being dragged as the drag initiator .

LISTING 10: Get and save the drag initiator.

      //Get the drag initiator component from the event
      // object and cast it to the correct type.
      var dragInitiator:Image = Image(
                                     event.currentTarget);

In this program, the drag initiator could be any of the three images shown in Figure 1 and Figure 3.

The code in Listing 10

Gets a reference to the Image object that dispatched the mouseDown event from the incoming method parameter
Casts it to type Image , and
Saves it in the variable named dragInitiator .

Populate a DragSource object with a copy of the image being dragged

Here is part of what the documentation has to say about the DragSource class.

"The DragSource class contains the data being dragged. The data can be in multiple formats, depending on the type of control that initiated the drag.
Each format of data is identified with a string. ... Data can be added directly using the addData() method, or indirectly using the addHandler() method."

Listing 11 adds the image being dragged to a new DragSource object and provides an identifier for the format as a string. You will see later how this string is used to establish the drop target.

LISTING 11: Populate a DragSource object with a copy of the image being dragged.

      var dragSource:DragSource = new DragSource();

      dragSource.addData(dragInitiator,"imageObject");

Initiate the drag and drop operation by calling the doDrag method

Listing 12 initiates the drag and drop operation by calling the static doDrag method of the DragManager class.

LISTING 12: Initiate the drag and drop operation by calling the doDrag method.

      DragManager.doDrag(dragInitiator,dragSource,event);

    }//end mouseDownHandler

What does the documentation have to say about the DragManager class?

Here is part of what the documentation has to say about the DragManager class.

"The DragManager class manages drag and drop operations, which let you move data from one place to another in a Flex application. For example, you can select an object, such as an item in a List control or a Flex control, such as an Image control, and then drag it over another component to add it to that component.
All methods and properties of the DragManager are static, so you do not need to create an instance of it. ...
When the user selects an item with the mouse, the selected component is called the drag initiator. The image displayed during the drag operation is called the drag proxy.
When the user moves the drag proxy over another component, the dragEnter event is sent to that component. If the component accepts the drag, it becomes the drop target and receives dragOver, dragExit, and dragDrop events.
When the drag is complete, a dragComplete event is sent to the drag initiator."

What about the doDrag method?

The documentation states simply that the doDrag method

"Initiates a drag and drop operation."

The doDrag method parameters

The doDrag method has several parameters with default values in addition to the three shown in Listing 12. Here is part of what the documentation has to say about the three parameters passed to the doDrag method in Listing 12.

dragInitiator :IUIComponent - IUIComponent that specifies the component initiating the drag.
dragSource :DragSource - DragSource object that contains the data being dragged.
event:MouseEvent - The MouseEvent that contains the mouse information from the start of the drag.

The end of the mouseDown event handler

Listing 12 signals the end of the mouseDown event handler. This leaves two more event handlers to be discussed. The remaining two event handlers were registered on the drop target ( Canvas object) by the code in Listing 8.

The dragEnter event handler

As you learned earlier , when the user moves the drag proxy over another component, that component dispatches a dragEnter event.

If a dragEnter event handler has been registered on that component, the handler method is executed. If the code in the event handler accepts the drag, it becomes the drop target and receives dragOver , dragExit , and dragDrop events.

In this case the intended drop target is the Canvas object and the event handler shown in Listing 13 is registered on that object.

LISTING 13: The dragEnter event handler.

    private function enterHandler(event:DragEvent):void{
      if (event.dragSource.hasFormat("imageObject")){
          DragManager.acceptDragDrop(
                             Canvas(event.currentTarget));
      } //end if
    } //end enterHandler

Confirm the correct format string

The code in Listing 13 checks to confirm that the format string in the DragSource object matches "imageObject" (see Listing 11). If so, it calls the static acceptDragDrop method on the DragManager class, passing a reference to itself as a parameter in the method call.

Accept the dragged object

The call to the acceptDragDrop method notifies the DragManager that the Canvas object is willing to accept the contents of the DragSource object being dropped onto itself.

Beginning of the dragDrop event handler

The dragDrop event handler was registered on the Canvas object in Listing 8. This method is executed after the Canvas object accepts the drag and the user releases the mouse button while the drag proxy is over the Canvas .

Correct the drop position for the image

The code in Listing 14 uses the current location of the mouse pointer along with the values stored in localX and localY to compute the new location for the upper-left corner of the image when it is dropped on the canvas.

(Recall that localX and localY contain the coordinates of the mouse pointer relative to the upper-left corner of the image when the mouseDown event was dispatched by the image and the drag and drop operation began.)

I explained the need for this position adjustment earlier .

LISTING 14: Beginning of the dragDrop event handler.

    private function dropHandler(event:DragEvent):void{      

      var cornerX:Number = (Canvas(event.currentTarget).
                                         mouseX) - localX;
      var cornerY:Number = (Canvas(event.currentTarget).
                                         mouseY) - localY;

Do the drop

Listing 15 checks to confirm that the location at which the upper-left corner of the image will be placed is within the bounds of the canvas on the left side and the top. If so, it sets the coordinates of the Image object that dispatched the original mouseDown event to the coordinates that were computed in Listing 14. This causes that Image object to move to the new position on the Canvas object.

LISTING 15: Do the drop.

      if((cornerX > 0.0) && (cornerY > 0.0)){
        Image(event.dragInitiator).x = cornerX;
        Image(event.dragInitiator).y = cornerY
      } //end if
    } //end dropHandler
    //--------------------------------------------------//
      
  } //end class
} //end package

The end of the program

Listing 15 also signals the end of the dragDrop event handler, the end of the Driver class, and the end of the program.

Run the program

I encourage you to run this program from the web. Then copy the code from Listing 16 and Listing 17. Use that code to create a Flex project. Compile and run the project. Experiment with the code, making changes, and observing the results of your changes. Make certain that you can explain why your changes behave as they do.

Resources

I will publish a list containing links to ActionScript resources as a separate document. Search for ActionScript Resources in the Connexions search box.

Complete program listings

Complete listings for the MXML and ActionScript code discussed in this lesson are provided in Listing 16 and Listing 17 below.

LISTING 16: The MXML file for DragAndDrop01.

<?xml version="1.0" encoding="utf-8"?>
<!--DragAndDrop01
-->

<mx:Application 
  xmlns:mx="http://www.adobe.com/2006/mxml" 
  xmlns:cc="CustomClasses.*">
  
  <cc:Driver/>

</mx:Application>

LISTING 17: The ActionScript file for DragAndDrop01.

/*DragAndDrop01
Illustrates the fundamentals of drag and drop in
ActionScript 3.

Places three images in a Canvas object:

0 - space.jpg - largest
1 - snowscene.jpg - midsize
2 - frog.jpg - smallest

Sets the z-axis indices as shown above. This causes the 
space image to be in the back, the frog image to be in the
front, and the snowscene image to be in the middle.

Any of the images can be dragged and dropped anywhere 
within the canvas so long as the mouse pointer doesn't 
leave the canvas. However, If the edge of the dragged 
image goes outside the left edge or the top of the canvas,
the drag and drop operation is aborted. If the dragged 
image goes outside the right side or the bottom of the 
canvas, scroll bars automatically appear on the canvas.

The size of the canvas is based on the size of the space
image so that other images can be substituted for mine 
when the program is recompiled so long as the file names 
and paths are the same.
*********************************************************/
package CustomClasses{
  import flash.events.MouseEvent;
  
  import mx.containers.Canvas;
  import mx.controls.Image;
  import mx.core.DragSource;
  import mx.events.DragEvent;
  import mx.events.FlexEvent;
  import mx.managers.DragManager;

  //====================================================//
  
  public class Driver extends Canvas {
    private var imageA:Image = new Image();
    private var imageB:Image = new Image();
    private var imageC:Image = new Image();
    private var localX:Number;
    private var localY:Number;
    
    public function Driver(){//constructor
      //Make the Canvas visible.
      setStyle("backgroundColor",0x00FFFF);
      setStyle("backgroundAlpha",1.0);

      //Embed the image files in the SWF file.
      [Embed("snowscene.jpg")]
      var imgA:Class;
      
      [Embed("space.jpg")]
      var imgB:Class;
      
      [Embed("frog.jpg")]
      var imgC:Class;
      
      //Load the images from the embedded image files
      // into the Image objects.
      imageA.load(imgA);
      imageB.load(imgB);
      imageC.load(imgC);
      
      // Set the z-axes indices such that the frog is
      // in front, the snowscene is in the middle and the 
      // space image is at the back.
      addChildAt(imageB,0);//set index to 0
      addChildAt(imageA,1);//set index to 1
      addChildAt(imageC,2);//set index to 2

      //Register an event handler that will be executed
      // whcn the canvas and its children are fully 
      // constructed.
      this.addEventListener(FlexEvent.CREATION_COMPLETE,
                                         completeHandler);
    } //end constructor
    //--------------------------------------------------//

    //This handler method is executed when the Canvas and
    // its children have been fully created.
    private function completeHandler(
                          event:mx.events.FlexEvent):void{
      //Set the width and height of the canvas based on 
      // the dimensions of imageB.
      this.width = 1.3*imageB.width;
      this.height = 1.3*imageB.height;
      
      //Register event listeners to support drag and drop 
      // operations on all three images with the canvas
      // as the drag target.
      imageA.addEventListener(MouseEvent.MOUSE_DOWN,
                                        mouseDownHandler);
      imageB.addEventListener(MouseEvent.MOUSE_DOWN,
                                        mouseDownHandler);
      imageC.addEventListener(MouseEvent.MOUSE_DOWN,
                                        mouseDownHandler);
      
      this.addEventListener(DragEvent.DRAG_DROP,
                                             dropHandler);
      this.addEventListener(DragEvent.DRAG_ENTER,
                                        enterHandler);
    } //end completeHandler
    //--------------------------------------------------//
    
    // This event handler initiates the drag-and-drop \
    // operation for the image that dispatches the 
    // mouseDown event.
    private function mouseDownHandler(
                                   event:MouseEvent):void{

      //Save the location of the mouse within the image
      // being dragged. This information will be used
      // later to properly position the dropped image in
      // the drop target.
      this.localX = event.localX;
      this.localY = event.localY;

      //Get the drag initiator component from the event
      // object and cast it to the correct type.
      var dragInitiator:Image = Image(
                                     event.currentTarget);

      //Add the image being dragged to a DragSource
      // object and define an identifier as a string.
      var dragSource:DragSource = new DragSource();
      dragSource.addData(dragInitiator,"imageObject");
           
      //Call the static doDrag method on the DragManager
      // class to manage the overall drag and drop 
      // operation.
      DragManager.doDrag(dragInitiator,dragSource,event);
    }//end mouseDownHandler
    //--------------------------------------------------//
    
    //This dragEnter event handler causes the canvas to
    // be a suitable drop target.
    private function enterHandler(event:DragEvent):void{
      if (event.dragSource.hasFormat("imageObject")){
          DragManager.acceptDragDrop(
                             Canvas(event.currentTarget));
      } //end if
    } //end enterHandler
    //--------------------------------------------------//
    
    //Execute the dragDrop event handler to drop the image
    // in its new location. Compensate for the fact that
    // the mouse pointer is not at the upper-left corner 
    // of the image. Also don't allow the image to be 
    // dragged off the left side of the canvas or off the 
    // top of the canvas.
    private function dropHandler(event:DragEvent):void{
      
      //Compute the position of the upper-left corner of
      // the dropped image.
      var cornerX:Number = (Canvas(event.currentTarget).
                                         mouseX) - localX;
      var cornerY:Number = (Canvas(event.currentTarget).
                                         mouseY) - localY;
      if((cornerX > 0.0) && (cornerY > 0.0)){
        Image(event.dragInitiator).x = cornerX;
        Image(event.dragInitiator).y = cornerY
      } //end if
    } //end dropHandler
    //--------------------------------------------------//
      
  } //end class
} //end package