Worker Threads and SwingWorker

When a Swing program needs to execute a long-running task, it usually uses one of the worker threads, also known as the background threads. Each task running on a worker thread is represented by an instance of javax.swing.SwingWorker. SwingWorker itself is an abstract class; you must define a subclass in order to create a SwingWorker object; anonymous inner classes are often useful for creating very simple SwingWorker objects.

SwingWorker provides a number of communication and control features:

• The SwingWorker subclass can define a method, done, which is automatically invoked on the event dispatch thread when the background task is finished.
• SwingWorker implements java.util.concurrent.Future. This interface allows the background task to provide a return value to the other thread. Other methods in this interface allow cancellation of the background task and discovering whether the background task has finished or been cancelled.
• The background task can provide intermediate results by invoking SwingWorker.publish, causing SwingWorker.process to be invoked from the event dispatch thread.
• The background task can define bound properties. Changes to these properties trigger events, causing event-handling methods to be invoked on the event dispatch thread.

These features are discussed in the following subsections.