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  • “write once, run anywhere” -> “compile once, run anywhere”

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  • 1. Why Java? A brief introduction to Java and its features Prepared by Nyversity
  • 2. Java is…  A general purpose, high-level programming language with support for object-oriented programming.  A collection of wide-ranging application programming interfaces (APIs).  A self-contained runtime system.  A complete set of development tools.
  • 3. Java is not…  An internet-only programming language.  Difficult.  JavaScript.
  • 4. Java’s Main Features  Uses virtual machine model to assure true “write once, run anywhere” programs.  Built-in support for GUIs.  Built-in networking.  Built-in security features.  Built-in support for multi-threaded programming.  Self-documenting.
  • 5. Java applications  Applets  Stand-alone programs  Network servers  Network clients  Embedded designs  Mobile telephones  Portable Digital Assistants (PDAs)  Set-top boxes  Digital Signal Processing (DSP)
  • 6. Java Virtual Machine  The conventional compiled-code model source code compiler/ linker object code (native) object code Microprocessor system
  • 7. Java Virtual Machine  The virtual machine model source code compiler/ linker bytecode bytecode Microprocessor system Java Virtual Machine
  • 8. Java Virtual Machine Advantages  Compiled bytecode can run without modification on any platform that has a Java Virtual Machine.  “Compile once, run anywhere”.
  • 9. Java Virtual Machine Disadvantages  Compiled bytecode runs a little slower than conventional compiled code.  Advances in JVM technology are closing the gap.  Not all low-level system manipulations are available through standard Java APIs.  Low-level system manipulations are available in the form of native (non-Java) extensions.
  • 10. Java Language Features  Syntax is similar to C++.  Full support for OOP  Classes and objects  Information hiding/access control  Inheritance, method overriding  Polymorphism  Abstract methods and classes  Interfaces
  • 11. Java Language Features  Everything that is not a primitive is an object.  No pointers! Objects are accessed through reference variables.  Built-in memory management and garbage collection.
  • 12. Java API Features  Support for the essentials  Classes and objects  I/O  Threads  Applet support  Conventions used by applets
  • 13. Java API Features  Graphic User Interface (GUI) support  Abstract Windowing Toolkit (AWT)  Windows, dialogs, file dialogs  Buttons, checkboxes  Menus, menu bars  Scrollbars  etc.  New generation GUI toolkit: Swing  All the above, plus...  Platform independent and run-time changeable look-and-feel.  And more.
  • 14. Java API Features  Networking  TCP/IP  UDP  URLs  Internationalization  Programs can automatically adapt to specific locales and be displayed in the appropriate language.
  • 15. Java API Features  Security  Electronic signatures  Public and private key management  Access control  Certificates  Java Database Connectivity (JDBCTM )  Provides uniform access to a wide range of relational databases.
  • 16. Java API Features  The Java platform also has APIs for  2D and 3D graphics  Accessibility  Servers  Collaboration  Telephony  Speech  Animation  and more.
  • 17. Benefits of Programming in Java  Get started quickly Although the Java programming language is a powerful object-oriented language, it's easy to learn, especially for programmers already familiar with C or C++.  Write less code Comparisons of program metrics suggest that a program written in the Java programming language can be four times smaller than the same program in C++.
  • 18. Benefits of Programming in Java  Write better code  The Java programming language encourages good coding practices.  Garbage collection helps you avoid memory leaks.  Its object orientation and wide-ranging, easily extendible API let you reuse other people's tested code and introduce fewer bugs.
  • 19. Benefits of Programming in Java  Develop programs faster Development time may be as much as twice as fast compared to writing the same program in C++ because you write fewer lines of code and it is a simpler programming language than C++.
  • 20. Benefits of Programming in Java  Avoid platform dependencies. You can keep your program portable by avoiding the use of libraries written in other languages and native methods.  Write once, run anywhere. Because 100% pure Java programs are compiled into machine-independent bytecodes, they run consistently on any Java platform.
  • 21. Benefits of Programming in Java  Distribute software more easily. Upgrade applets easily from a central server. Applets take advantage of the feature of allowing new classes to be loaded "on the fly," without recompiling the entire program.