Demonstration of final variables : final « Class Definition « Java Tutorial

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Java Tutorial » Class Definition » final 
5.27.12.Demonstration of final variables
/*
 *     file: FinalVariables.java
 *  package: oreilly.hcj.finalstory
 *
 * This software is granted under the terms of the Common Public License,
 * CPL, which may be found at the following URL:
 * http://www-124.ibm.com/developerworks/oss/CPLv1.0.htm
 *
 * Copyright(c) 2003-2005 by the authors indicated in the @author tags.
 * All Rights are Reserved by the various authors.
 *
########## DO NOT EDIT ABOVE THIS LINE ########## */


import javax.swing.JDialog;

/**  
 * Demonstration of final variables.
 *
 @author <a href=mailto:[email protected]>Robert Simmons jr. (kraythe)</a>
 @version $Revision: 1.3 $
 */
public class FinalVariables {
  /** 
   * Test code.
   *
   @param args Command line arguments.
   */
  public static final void main(final String[] args) {
    System.out.println("Note how the key variable is changed.");
    someMethod("JAVA_HOME");
    someMethod("ANT_HOME");
  }

  /** 
   * Get an environment property.
   *
   @param environmentKey The key to an environment property.
   *
   @return The value of the property.
   */
  public static String someBuggedMethod(final String environmentKey) {
    final String key = "env." + environmentKey;
    System.out.println("Key is: " + key);
    // key = new String("someValue"); // <= compiler error.  
    return (System.getProperty(key));
  }

  /** 
   * Get an environment property.
   *
   @param environmentKey The key to an environment property.
   *
   @return The value of the property.
   */
  public static String someMethod(final String environmentKey) {
    final String key = "env." + environmentKey;
    System.out.println("Key is: " + key);
    return (System.getProperty(key));
  }

  /** 
   * build the panel that comprises the dialog.
   *
   @param name The name of the instance.
   */
  public void buildGUIDialog(final String name) {
    final String instanceName;
    if (name == null) {
      // no problem here.
      instanceName = getClass()
                       .getName() + hashCode();
    else {
      // no problem here as well.
      instanceName = getClass()
                       .getName() + name;
    }

    JDialog dialog = new JDialog();

    // .. Do a bunch of layout and component building. 
    dialog.setTitle(instanceName);

    // .. Do dialog assembly
    // instanceName = "hello";  // <= compiler error
  }
}

/* ########## End of File ########## */
5.27.final
5.27.1.final Variables
5.27.2.'Blank' final fields
5.27.3.Java Final variable: Once created and initialized, its value can not be changed
5.27.4.Using 'final' with method arguments
5.27.5.The effect of final on fields
5.27.6.You can override a private or private final method
5.27.7.Making an entire class final
5.27.8.Demonstrates how final variables are replaced at compilation time
5.27.9.Demonstration of final class members
5.27.10.Base class for demonstation of final methods
5.27.11.Demonstration of final constants
5.27.12.Demonstration of final variables
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