JAVA user custom event listener instance code

JAVA user custom event listener instance code

Many user-defined events are introduced without examples, or examples are incomplete, the following is a complete example, and written comments for reference, complete example source code is as follows:

package demo;
import Java.util.EventObject;
/**
* Title:  Event handler class, which inherits the event base class 
* Description: 
* Copyright: Copyright (c) 2005
* Company: cuijiang
* @author not attributable
* @version 1.0
*/
public class DemoEvent extends EventObject
{
  private Object obj;
  private String sName;
  public DemoEvent(Object source,String sName)  {
   super(source);
   obj = source;
   this.sName=sName;
  }
  public Object getSource()
  {
   return obj;
  }
  public void say()
  {
   System.out.println(" This is a  say  methods ...");
  }
  public String getName()
  {
   return sName;
  }
}

package demo;
import java.util.EventListener;
/**
* Title:  Listener interface 
* Description: 
* Copyright: Copyright (c) 2005
* Company: cuijiang
* @author not attributable
* @version 1.0
*/
public interface DemoListener extends EventListener{
  public void demoEvent(DemoEvent dm);
}
 

package demo;
import java.util.*;
/**
* Title:  Classes that use events 
* Description:  This class implements the addition of listeners and the execution of listener methods, and the execution of events due to property changes 
* Description:  Pay attention to synchronization when adding, deleting, and executing listeners 
* Copyright: Copyright (c) 2005
* Company: cuijiang
* @author not attributable
* @version 1.0
*/
public class DemoSource{
  private Vector repository = new Vector();
  private DemoListener dl;
  private String sName="";
  public DemoSource()
  {
  }
  // Register listeners if not used here Vector It USES ArrayList So pay attention to synchronization 
  public void addDemoListener(DemoListener dl)
  {
   repository.addElement(dl);// Pay attention to synchronization in this step 
  }
  // If it's not used here Vector It USES ArrayList So pay attention to synchronization 
  public void notifyDemoEvent(DemoEvent event) {
   Enumeration enum = repository.elements();// Pay attention to synchronization in this step 
   while(enum.hasMoreElements())
   {
    dl = (DemoListener)enum.nextElement();
    dl.demoEvent(event);
   }
  }
  // Delete listener if not used here Vector It USES ArrayList So pay attention to synchronization 
  public void removeDemoListener(DemoListener dl)
  {
   repository.remove(dl);// Pay attention to synchronization in this step 
  }
  /**
  *  Set properties 
  * @param str1 String
  */
  public void setName(String str1)
  {
   boolean bool=false;
   if(str1==null && sName!=null) bool=true;
   else if(str1!=null && sName==null) bool=true;
   else if(!sName.equals(str1)) bool=true;
   this.sName=str1;
   // If the change is made, the event is executed 
   if(bool) notifyDemoEvent(new DemoEvent(this,sName));
  }
  public String getName()
  {
   return sName;
  }
}
 

package demo;
import java.lang.Thread;
/**
* Title:  The test class 
* Description:  Test the occurrence of an event caused by a property change 
* Copyright: Copyright (c) 2005
* Company: cuijiang
* @author not attributable
* @version 1.0
*/
public class TestDemo
   implements DemoListener {
  private DemoSource ds;
  public TestDemo()
  {
   ds=new DemoSource();
   ds.addDemoListener(this);
   System.out.println(" Finished adding listeners ");
   try {
    Thread.sleep(3000);
    // Change attributes , Triggering event 
    ds.setName(" Change attributes , Triggering event ");
   }
   catch (InterruptedException ex) {
    ex.printStackTrace();
   }
   ds.addDemoListener(this);
   System.out.println(" Finished adding listeners 2");
   try {
    Thread.sleep(3000);
    // Change attributes , Triggering event 
    ds.setName(" Change attributes , Triggering event 2");
   }
   catch (InterruptedException ex) {
    ex.printStackTrace();
   }
   ds.removeDemoListener(this);
   System.out.println(" Finished adding listeners 3");
   try {
    Thread.sleep(3000);
    // Change attributes , Triggering event 
    ds.setName(" Change attributes , Triggering event 3");
   }
   catch (InterruptedException ex) {
    ex.printStackTrace();
   }

  }
  public static void main(String args[])
  {
   new TestDemo();
  }
  /**
  * demoEvent
  *
  * @param dm DemoEvent
  * @todo Implement this test.DemoListener method
  */
  public void demoEvent(DemoEvent dm) {
   System.out.println(" Event handling method ");
   System.out.println(dm.getName());
   dm.say();
  }
}

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