Java Terms

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Java Terms

• Middle Tennessee State University
• Fall, 2005

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Java Terms

• Java Application Program program that is stored
  and run on a users local computer.
• Has a method called main()
• Stored and run on users local computer
• May be command-line or GUI interface
• Java Applet java program that is embedded in a
  Web page.
• No method called main()
• Methods are called by browser

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Java Terms

• JSDK Java Software Development Kit (also called
  JDK for Java Development Kit)
• Primitive command-line tool set that includes
  libraries, compiler, interpreter and applet
  viewer for testing Java applets as well as other
  useful utilities
• IDE Integrated Development Environment
• Java development package for rapid development of
  Java programs (edit, compile, build, debug)
• Effort if required to learn how to use
• JBuilder by Borland (www.borland.com/)
• Eclipse Open Source by IBM (www.eclipse.org)
• NetBeans OpenSource by Sun (www.netbeans.org)
• BlueJ - www.blueJ.org (free download)
• JGrasp www.jgrasp.com (free download)

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Java Terms

• Java Class Library predefined classes
• Java is a object oriented language
• Use classes to set up objects
• Java programs consist of the use of many classes
• Java APIs Java Application Programming
  Interfaces
• Collection of existing classes in the Java class
  library

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Terms - Creating a Java Program

• Javac Java compiler that translates Java source
  code into bytecode
• Bytecode is the language that is understood only
  by a Java interpreter
• Is not machine language for any particular
  computer
• Language for a fictitious computer called Java
  Virtual Machine
• Each computer will have its own bytecode
  interpreter
• Bytecode interpreters are very simple compared to
  a compiler

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Example - compilation

• Source file Welcome.java
• To translate to bytecode javac Welcome.java
• Result of translation produces a file called
  Welcome.class (bytecode)
• To execute java Welcome

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Terms

• JVM Java virtual machine interpreter for Java
  bytecode
• appletviewer program used as a debugging aid
  when creating Java applets

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Terms

• Package group of related classes pre-defined by
  Java
• Java class Library set of all packages
• Core package
• Name of package begins with java
• Example the java.lang package

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Terms

• Optional packages
• Name of package begins with javax
• Example the javax.swing package
• Many packages are included in JSDK

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Predefined classes

• System
• Class defined in java.lang package
• String
• Class defined in the java.lang package
• JOptionPane
• Class defined in the javax.swing package
• Creates dialog boxes

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Typical Java Environment

• Phase I Create source program with an editor
  and save with .java extension
• File name must be the same as the class name
• Phase 2 Compile using javac
• Produces bytecode with .class extension
• Phase 3 Loader puts .class files in memory
• Phase 4 Bytecode Verifier checks validity of
  bytecode
• Phase 5 - Interpreter

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Java Conventions

• Class names begin with uppercase letter and
  multiple word names are capitalized
• Example public class Welcome
• Example public class WelcomeLetter
• File names must be identical to class name
• Programs have one public class only.
• Variables begin with lower case letters

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Writing a Java Program

• Two types of programs
• Application programs
• Applets
• Application programs
• Standalone programs
• Can be executed from any computer with a Java
  interpreter
• Applets
• Special type of java program that can run
  directly from a Java-compatible Web browser

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Java Application Program

• Comments
• //This is a Java comment
• / This is a Java comment /
• / this is a Java comment /
• Preferred method in certain cases
• / This is best! We will find out why later!/
• Called a javadoc comment
• Used for documenting classes, etc

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Java Modifiers

• Reserved words that specify properties of data,
  methods, and classes
• public
• static
• private
• final
• abstract
• protected

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Statements/Blocks/Methods

• Every Java statement ends with a semicolon.
• Blocks begin with and end with
• Method collections of statements that perform a
  sequence of operations
• Classes normally contain 1 or more methods
• main Method (required) for Java Applications
• //form of the main method
• public static void main (String args)
• / statements

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Example 1

• /
• The following Java Application program displays
  a welcome message to the standard output.
• /
• public class Welcome
• public static void main (String args)
• //Display a welcome message
• System.out.println(Welcome to the world of
  Java!)

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Example 2

• public class Welcome
• public static void main (String args)
• //Display a welcome message
• displayMessage()
• public static void displayMessage()
• System.out.println(Welcome \n to the world of
  Java!)

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Good Web Sites

• http//java.sun.com/j2se/1.5.0/docs/api/overview-s
  ummary.html
• http//java.sun.com/docs/books/tutorial/java/
• http//java.sun.com/docs/books/tutorial/java/TOC.h
  tml

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The End