/*** Desc:Fork/Join框架的目的是以递归方式将可以并行的任务拆分为更小的任务，然后将每个子任务的结果合并起来生成一个整体结果。* 要把任务提交到ForkJoinPool必须创建RecursiveTask<T> 的一个子类* * @author wei.zw* @since 2016年7月6日 下午9:27:56* @version v 0.1*/
public class ForkJoinSumCalculator extends RecursiveTask<Long> {/**  */private static final long serialVersionUID = -8013303660374621470L;private final long[] numbers;private final int start;private final int end;private static final long THRESHOLD = 1000;/*** @param numbers* @param start* @param end*/public ForkJoinSumCalculator(long[] numbers, int start, int end) {super();this.numbers = numbers;this.start = start;this.end = end;}/*** @param numbers*/public ForkJoinSumCalculator(long[] numbers) {super();this.numbers = numbers;this.start = 0;this.end = numbers.length;}/*** @see java.util.concurrent.RecursiveTask#compute()*/@Overrideprotected Long compute() {int length = end - start;if (length <= THRESHOLD) {return computeSequentially();}ForkJoinSumCalculator leftTask = new ForkJoinSumCalculator(numbers, start, start + length / 2);leftTask.fork();ForkJoinSumCalculator rightTask = new ForkJoinSumCalculator(numbers, start + length / 2, end);rightTask.fork();Long rightResult = 0L;try {rightResult = rightTask.get();} catch (Exception e) {}Long leftResult = leftTask.join();return leftResult + rightResult;}/*** * @return* @author wei.zw*/private Long computeSequentially() {long sum = 0;for (int i = start; i < end; i++) {sum += numbers[i];}return sum;}public static void main(String[] args) {long[] numbers = LongStream.rangeClosed(1, 10000000).toArray();long start = System.currentTimeMillis();System.out.println(new ForkJoinPool().invoke(new ForkJoinSumCalculator(numbers)) + " 耗时："+ (System.currentTimeMillis() - start));}}

/*** @see java.util.concurrent.RecursiveTask#compute()*/@Overrideprotected Long compute() {int length = end - start;if (length <= THRESHOLD) {return computeSequentially();}ForkJoinSumCalculator leftTask = new ForkJoinSumCalculator(numbers, start, start + length / 2);leftTask.fork();ForkJoinSumCalculator rightTask = new ForkJoinSumCalculator(numbers, start + length / 2, end);Long rightResult = rightTask.compute();Long leftResult = leftTask.join();return leftResult + rightResult;}

public abstract class RecursiveTask<V> extends ForkJoinTask<V> {private static final long serialVersionUID = 5232453952276485270L;//计算结果V result;//抽象的计算方法protected abstract V compute();//获取计算结果public final V getRawResult() {return result;}//设置计算结果protected final void setRawResult(V value) {result = value;}//执行计算protected final boolean exec() {result = compute();return true;}}