实现ThreadFactory接口生成自定义的线程给Fork/Join框架

　　Fork/Join框架是Java7中最有趣的特征之一。它是Executor和ExecutorService接口的一个实现，允许你执行Callable和Runnable任务而不用管理这些执行线程。这个执行者面向执行能被拆分成更小部分的任务。主要组件如下：

• 一个特殊任务，实现ForkJoinTask类
• 两种操作，将任务划分成子任务的fork操作和等待这些子任务结束的join操作
• 一个算法，优化池中线程的使用的work-stealing算法。当一个任务正在等待它的子任务（结束）时，它的执行线程将执行其他任务（等待执行的任务）。

　 ForkJoinPool类是Fork/Join的主要类。在它的内部实现，有如下两种元素：

• 一个存储等待执行任务的列队。
• 一个执行任务的线程池

　　在这个指南中，你将学习如何实现一个在ForkJoinPool类中使用的自定义的工作者线程，及如何使用一个工厂来使用它。

　  要自定义ForkJoinPool类使用的线程，必须继承ForkJoinWorkerThread

public class MyWorkerThread extends ForkJoinWorkerThread {
	private static ThreadLocal<Integer> taskCounter = new ThreadLocal<Integer>();
	protected MyWorkerThread(ForkJoinPool pool) {
		super(pool);
	}
	@Override
	protected void onStart() {
		super.onStart();
		System.out.println("MyWorkerThread " + getId()+ " : Initializing task counter");
		taskCounter.set(0);
	}
	@Override
	protected void onTermination(Throwable exception) {
		System.out.println("MyWorkerThread " + getId() + " :"
				+ taskCounter.get());
		super.onTermination(exception);
	}
	public void addTask() {
		int counter = taskCounter.get().intValue();
		counter++;
		taskCounter.set(counter);
	}	
}

 　　继承ForkJoinWorkerThreadFactory创建MyWorkerThreadFactory工厂

public class MyWorkerThreadFactory implements ForkJoinWorkerThreadFactory {
	@Override
	public MyWorkerThread newThread(ForkJoinPool pool) {
		return new MyWorkerThread(pool);
	}
}

public class MyRecursiveTask extends RecursiveTask<Integer> {
	private int array[];
	private int start, end;
	public MyRecursiveTask(int[] array, int start, int end) {
		super();
		this.array = array;
		this.start = start;
		this.end = end;
	}
	@Override
	protected Integer compute() {
		Integer ret;
		MyWorkerThread thread = (MyWorkerThread) Thread.currentThread();
		thread.addTask();
		if (end - start > 100) {
			int mid = (start + end) / 2;
			MyRecursiveTask task1 = new MyRecursiveTask(array, start, mid);
			MyRecursiveTask task2 = new MyRecursiveTask(array, mid, end);
			invokeAll(task1, task2);
			ret = addResults(task1, task2);
		} else {
			int add = 0;
			for (int i = start; i < end; i++) {
				add += array[i];
			}
			ret = new Integer(add);
		}
		try {
			TimeUnit.MILLISECONDS.sleep(10);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		return ret;
	}

	private Integer addResults(MyRecursiveTask task1, MyRecursiveTask task2) {
		int value = 0;
		try {
			value = task1.get().intValue() + task2.get().intValue();
		} catch (Exception e) {
			e.printStackTrace();
		}
		try {
			TimeUnit.MILLISECONDS.sleep(10);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return value;
	}
}

public class ForkMain {
	public static void main(String[] args) throws Exception {
		MyWorkerThreadFactory factory=new MyWorkerThreadFactory();
		ForkJoinPool joinPool=new ForkJoinPool(4, factory, null, false);
		int array[]=new int[100000];
		for (int i =0; i <100000; i++) {
			array[i]=i;
		}
		MyRecursiveTask task=new MyRecursiveTask(array, 0, 10000);
		joinPool.execute(task);
		task.join();
		joinPool.shutdown();
		joinPool.awaitTermination(1, TimeUnit.DAYS);
		System.out.println("Main: Result:"+task.get());
		System.out.println("Main:Ends");
	}
}