A simple demo of Observable and Observer : Observer Pattern « Design Pattern « Java





A simple demo of Observable and Observer

  
/*
 * Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
 * All rights reserved. Software written by Ian F. Darwin and others.
 * $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
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 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
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 * POSSIBILITY OF SUCH DAMAGE.
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 * Java, the Duke mascot, and all variants of Sun's Java "steaming coffee
 * cup" logo are trademarks of Sun Microsystems. Sun's, and James Gosling's,
 * pioneering role in inventing and promulgating (and standardizing) the Java 
 * language and environment is gratefully acknowledged.
 * 
 * The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
 * inventing predecessor languages C and C++ is also gratefully acknowledged.
 */

import java.util.Observable;
import java.util.Observer;

/**
 * A simple demo of Observable->Observer
 * 
 * @author Ian Darwin
 * @version $Id: ObservDemo.java,v 1.3 2003/12/29 19:52:22 ian Exp $
 */
public class ObservDemo extends Object {
  MyView view;

  MyModel model;

  public ObservDemo() {

    view = new MyView();

    model = new MyModel();
    model.addObserver(view);

  }

  public static void main(String[] av) {
    ObservDemo me = new ObservDemo();
    me.demo();
  }

  public void demo() {
    model.changeSomething();
  }

  /** The Observer normally maintains a view on the data */
  class MyView implements Observer {
    /** For now, we just print the fact that we got notified. */
    public void update(Observable obs, Object x) {
      System.out.println("update(" + obs + "," + x + ");");
    }
  }

  /** The Observable normally maintains the data */
  class MyModel extends Observable {
    public void changeSomething() {
      // Notify observers of change
      setChanged();
      notifyObservers();
    }
  }
}



           
         
    
  










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