Task.java

package mapwriter;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;

public abstract class Task implements Runnable {
	
	// the task stores its own future
	private Future<?> future = null;

	// called by processTaskQueue after the thread completes
	public abstract void onComplete();
	
	// the method that runs in a separate thread
	// must not access future in run()
	public abstract void run();
	
	// methods to access the tasks Future variable
	public final Future<?> getFuture() {
		return this.future;
	}
	
	public final void setFuture(Future<?> future) {
		this.future = future;
	}
	
	public final boolean isDone() {
		return (this.future != null) ? this.future.isDone() : false;
	}
	
	public final void printException() {
		if (this.future != null) {
			try {
				this.future.get();
			} catch (ExecutionException e) {
				Throwable rootException = e.getCause();
				rootException.printStackTrace();
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
	}
}