Repository navigation
Expand file tree
/
Copy pathCountTask.java
More file actions
80 lines (72 loc) · 2.4 KB
/
Copy pathCountTask.java
File metadata and controls
80 lines (72 loc) · 2.4 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
package chapter06;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.Future;
import java.util.concurrent.RecursiveTask;
/**
* 计数器任务
*
* @author tengfei.fangtf
* @version $Id: CountTask.java, v 0.1 2015-8-1 上午12:00:29 tengfei.fangtf Exp $
*/
public class CountTask extends RecursiveTask<Integer> {
/**
*
*/
private static final long serialVersionUID = -7026164332281366252L;
private static final int THRESHOLD = 2; // 阈值
private int start;
private int end;
public CountTask(int start, int end) {
this.start = start;
this.end = end;
}
@Override
protected Integer compute() {
int sum = 0;
// 如果任务足够小就计算任务
boolean canCompute = (end - start) <= THRESHOLD;
if (canCompute) {
for (int i = start; i <= end; i++) {
sum += i;
}
} else {
// 如果任务大于阈值，就分裂成两个子任务计算
int middle = (start + end) / 2;
CountTask leftTask = new CountTask(start, middle);
CountTask rightTask = new CountTask(middle + 1, end);
//执行子任务
leftTask.fork();
rightTask.fork();
//等待子任务执行完，并得到其结果
int leftResult = leftTask.join();
int rightResult = rightTask.join();
//合并子任务
sum = leftResult + rightResult;
}
return sum;
}
public static void main(String[] args) {
long t1 = System.nanoTime();
ForkJoinPool forkJoinPool = new ForkJoinPool();
// 生成一个计算任务，负责计算1+2+3+4
CountTask task = new CountTask(1,40);
// 执行一个任务
Future<Integer> result = forkJoinPool.submit(task);
try {
System.out.println(result.get());
} catch (InterruptedException e) {
} catch (ExecutionException e) {
}
long t2 = System.nanoTime();
System.out.println(t2-t1);
long t3 = System.nanoTime();
int sum = 0;
for(int i=1;i<=40;i++) {
sum = sum+i;
}
System.out.println(sum);
long t4 = System.nanoTime();
System.out.println(t4-t3);
}
}