?? swingworker.java
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package com.bbn.openmap.util;import javax.swing.SwingUtilities;/** * This is the 3rd version of SwingWorker (also known as SwingWorker * 3), an abstract class that you subclass to perform GUI-related work * in a dedicated thread. For instructions on using this class, see: * * http://java.sun.com/docs/books/tutorial/uiswing/misc/threads.html * * Note that the API changed slightly in the 3rd version: You must now * invoke start() on the SwingWorker after creating it. */public abstract class SwingWorker { private Object value; // see getValue(), setValue() /** * Class to maintain reference to current worker thread under * separate synchronization control. */ private static class ThreadVar { private Thread thread; ThreadVar(Thread t) { thread = t; } synchronized Thread get() { return thread; } synchronized void clear() { thread = null; } } private ThreadVar threadVar; /** * Get the value produced by the worker thread, or null if it * hasn't been constructed yet. */ protected synchronized Object getValue() { return value; } /** * Set the value produced by worker thread */ private synchronized void setValue(Object x) { value = x; } /** * Compute the value to be returned by the <code>get</code> * method. */ public abstract Object construct(); /** * Called on the event dispatching thread (not on the worker * thread) after the <code>construct</code> method has returned. */ public void finished() {} /** * A new method that interrupts the worker thread. Call this * method to force the worker to stop what it's doing. */ public void interrupt() { Thread t = threadVar.get(); if (t != null) { t.interrupt(); } threadVar.clear(); } /** * Return the value created by the <code>construct</code> * method. Returns null if either the constructing thread or the * current thread was interrupted before a value was produced. * * @return the value created by the <code>construct</code> * method */ public Object get() { while (true) { Thread t = threadVar.get(); if (t == null) { return getValue(); } try { t.join(); } catch (InterruptedException e) { Thread.currentThread().interrupt(); // propagate return null; } } } /** * Start a thread that will call the <code>construct</code> * method and then exit. */ public SwingWorker() { final Runnable doFinished = new Runnable() { public void run() { finished(); } }; Runnable doConstruct = new Runnable() { public void run() { try { setValue(construct()); } finally { threadVar.clear(); } SwingUtilities.invokeLater(doFinished); } }; Thread t = new Thread(doConstruct); threadVar = new ThreadVar(t); } /** * Start the worker thread. */ public void start() { Thread t = threadVar.get(); if (t != null) { t.start(); } } /** * For compatibility with old versions of SwingWorker, calls * start(). */ public void execute() { start(); }}
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