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Introduction to Java

1. Introduction to Java. History of Java. Java Originally for intelligent consumer-electronic devices Then used for creating Web pages with dynamic content Now also used to: Develop large-scale enterprise applications Enhance WWW server functionality

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Introduction to Java

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  1. 1 • Introduction to Java

  2. History of Java • Java • Originally for intelligent consumer-electronic devices • Then used for creating Web pages with dynamic content • Now also used to: • Develop large-scale enterprise applications • Enhance WWW server functionality • Provide applications for consumer devices (cell phones, etc.)

  3. Java Class Libraries • Classes • Include methods that perform tasks • Return information after task completion • Used to build Java programs • Java provides class libraries • Known as Java APIs (Application Programming Interfaces)

  4. FORTRAN, COBOL, Pascal and Ada • FORTRAN • FORmula TRANslator • COBOL • COmmon Business Oriented Language • Pascal • Structured programming • Ada • Multitasking

  5. BASIC, Visual Basic, Visual C++, C# and .NET • BASIC • Beginner’s All-Purpose Symbolic Instruction Code • .NET • .NET platform • Visual Basic .NET • Based on BASIC • Visual C++ • Based on C++ • C# • Based on C++ and Java

  6. Typical Java Development Environment • Java programs normally undergo five phases • Edit • Programmer writes program (and stores program on disk) • Compile • Compiler creates bytecodes from program • Load • Class loader stores bytecodes in memory • Verify • Bytecode Verifier confirms bytecodes do not violate security restrictions • Execute • JVM translates bytecodes into machine language

  7. Fig. 1.1 Typical Java development environment.

  8. Creating a Program with JCreator • Click on the JCreator Icon • IDE windowappears

  9. Creating a Program with JCreator • Click on File, New, then Project • Project Wizard appears • Choose Java Application template

  10. Creating a Program with JCreator • Give the project a name • Then click Next

  11. At this point you can click on Finish Creating a Program with JCreator • You will want the JDK version 1.5 • This tab is where you can specify hsa library

  12. For now, you can proceed with Finish The Class Wizard appears. Specify a name for the class and make sure Public is chosen Creating a Program with JCreator • Now we create our class (the program) with File, New, and Class

  13. Creating a Program with JCreator • The wizard creates a template. • Now complete the program with the required commands.

  14. Build Output shows in bottom pane. This is where compiler error messages will be displayed. Creating a Program with JCreator • Run the compiler with Build, and CompileFile

  15. Creating a Program with JCreator • To run the compiled program click on Build, and ExecuteFile • Program runs in separate window Without Creating a Project

  16. Programming with "Ready to Program" • Find the "Ready" option on the program menu or click on the"Ready" icon

  17. Programming with "Ready to Program" • An empty editor window appears

  18. Classes consist of a collection of • Data items • Methods A Java class with a method called main() is a Java application. The name of the file and the name of the class must, that is MUST have the same name Java Programs • A Java program consists of one or more classes

  19. Creating a Java Application • The "Ready" environment will give you skeleton or boilerplate format for programs • Click on File, New, and HSA Console option • A dialog box asksfor the name of the class

  20. Bold Face Java keywords Black Identifiers in Java Class library GreenComments BlueIdentifiers in your program Creating a Java Application • The appropriate boilerplate text appears in the edit window – note the color coding RedQuoted Strings

  21. Note that a dialog box will ask you for the name • Be sure to give it exactly the same name as the class Creating a Java Application • Fill in the necessary commands • Save theprogram

  22. Creating a Java Application • To run a Java program • Press the Run button or • Press Ctrl+R or • Press F1 • The consoleprogram showsa consolewindow

  23. Creating a Java Application • Make sure to save the program before quitting • The "Ready" environment will remind you • To exit the "Ready" environment • Click the X close or • Choose File, Exit or • Use Ctrl-Q

  24. Dialog box shows how many errors Description of error given in the status bar Error line(s) highlighted Creating a Java Application • Errors in the program • Syntax errors are found for you by the compiler

  25. Why Different IDEs? • Which one you use depends on what you are doing • In class the Ready to Program IDE is easy to use, “quick and dirty” • But … it does not support JDK 5.0 • JCreator • supports JDK 5.0 • Eclipse • a bit more complicated, but does a bit more • found to be a bit balky with some elements of JDK 5.0

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