1 private class SumTask extends RecursiveTask<Long> {
2
3 private static final int THRESHOLD = 1250000;
4
5 private long arr[];
6 private int start;
7 private int end;
8
9 public SumTask(long[] arr, int start, int end) {
10 this.arr = arr;
11 this.start = start;
12 this.end = end;
13 }
14
15 /**
16 * 小计
17 */
18 private long subtotal() {
19 long sum = 0;
20 for (int i = start; i < end; i++) {
21 sum += arr[i];
22 }
23
24 return sum;
25 }
26
27 @Override
28 protected Long compute() {
29
30 if ((end - start) <= THRESHOLD) {
31 return subtotal();
32 }else {
33 int middle = (start + end) / 2;
34 SumTask left = new SumTask(arr, start, middle);
35 SumTask right = new SumTask(arr, middle, end);
36 left.fork();
37 right.fork();
38
39 return left.join() + right.join();
40 }
41 }
42 }
43
44 public static void main(String[] args) throws ExecutionException, InterruptedException{
45 int num = Runtime.getRuntime().availableProcessors();
46 long time = System.currentTimeMillis();
47 long[] arr = new long[10000000];
48 for (int i =0 ; i < 10000000; i++) {
49 arr[i] =i+1;
50 }
51
52 ForkJoinPool pool = new ForkJoinPool();
53 ForkJoinTask<Long> result = pool.submit(new ForkJoinTest().new SumTask(arr, 0, arr.length));
54 System.out.println("最终计算结果: " + result.invoke()+"耗时："+(System.currentTimeMillis() - time)+"，毫秒");
55 pool.shutdown();
56 }
