EnhancedThread makes Java threads more useful

A while back I wrote an application which spawned threads for lengthy import and export operations. I wanted to follow the thread progress using a popup progress bar. I wrote EnhancedThread to help make this possible and easy and generalized.

The most important addition is that a thread's state can be monitored by a listener. An EnhancedThread has the concept of progress, being stopped (paused), and being canceled. A thread also carries a mutable message. These features specifically make it easy to develop a GUI which displays the thread's progress, allows the user to pause, resume and cancel the task, displays messages from the thread to the user.

So in my case, I used an EnhancedThread to import collections of objects, which could take between, say, ten seconds and ten minutes. Along the way, I wanted to display a message indicating what object was currently being imported. Since several import threads could be running concurrently, I wanted to be able to pause, resume, and cancel them, so the user could prioritize their lengthy tasks.

Furthermore, I wanted to have a single window which displayed all threads, but I wanted that window to be monitor my application's master thread pool. The user only needed to see some threads, so EnhancedThread can indicate whether the thread is a user-visible thread, and can also explicitly signal the GUI that the thread manager window should be popped up for this thread. (Of course, that was only a flag, which the GUI could choose to ignore as appropriate.)

import java.util.EventListener;

import javax.swing.*;

import javax.swing.event.*;



/**

 * 

 * 

 * @author Nicholas R. Rinard

 */

public class EnhancedThread extends Thread {

 

    // ---- v a r i a b l e   d e c l a r a t i o n s ---------------------- //

 

 public static final String   messageProperty               = "__message_property__";

 public static final String   progressProperty              = "__progress_property__";

 

 private String               message                       = "";

 private double               progress                      = 0; // negative indicates indeterminate

 

 private boolean              canceledFlag                  = false;

 private boolean              stoppedFlag                   = false;

 

 // these public flags (no getters/setters) are clues to the GUI

 public boolean               isUserVisibleThread           = true;

 public boolean               threadRequestsVisibleWindow   = false;

 public boolean               threadCanBeCanceled           = true;

 

 private final EventListenerList allListeners               = new EventListenerList();

 

    // ---- p u b l i c   a p i -------------------------------------------- //

    

    /**

     * 

     */

    public EnhancedThread( String threadName, double threadProgress, String threadMessage ) {

  super( threadName );

  this.progress = threadProgress;

  this.message = threadMessage;

    }

 

 public void addChangeListener( ChangeListener l ) {

  if( l != null ) {

   allListeners.remove( ChangeListener.class, l );

   allListeners.add( ChangeListener.class, l );

  }

 }

 

 public double getProgress() {

  return this.progress;

 }

 

 public void setProgress( double newProgress ) {

  if( newProgress == this.progress ) return;

  this.progress = newProgress;

  fireStateChanged();

 }

 

 public String getMessage() {

  return this.message;

 }

 

 public void setMessage( String newMessage ) {

  if( newMessage.equals( this.message ) ) return;

  this.message = newMessage;

  fireStateChanged();

 }

 

 public void setCanceledFlag( boolean isCanceled ) {

  if( this.canceledFlag == isCanceled ) return;

  this.canceledFlag = isCanceled;

  fireStateChanged();

 }

 

 public boolean getCanceledFlag() {

  return this.canceledFlag;

 }

 

 public void setStoppedFlag( boolean isStopped ) {

  if( this.stoppedFlag == isStopped ) return;

  this.stoppedFlag = isStopped;

  fireStateChanged();

 }

 

 public boolean getStoppedFlag() {

  return this.stoppedFlag;

 }

 

 public String toString() {

  return "Thread{name=" + this.getName() + "; progress=" + this.getProgress() +"; message=" + this.getMessage() + "}";

 }

    

    // ---- p r i v a t e   c o n v e n i e n c e   m e t h o d s ---------- //

 

 private void fireStateChanged() {

  EventListener [] listeners = this.allListeners.getListeners( ChangeListener.class );

  for( int i = 0; i < listeners.length; i++ ) {

   ChangeListener listener = (ChangeListener) listeners[ i ];

   ChangeEvent e = new ChangeEvent( this );

   listener.stateChanged( e );

  }

 }

}