1+ package edu .maskleo .module1 ;
2+ 3+ import java .util .concurrent .ExecutionException ;
4+ import java .util .concurrent .ForkJoinPool ;
5+ import java .util .concurrent .Future ;
6+ import java .util .concurrent .RecursiveTask ;
7+ 8+ public class CountTaskForkJoinTest extends RecursiveTask <Long > {
9+ 10+ private static final long serialVersionUID = 1L ;
11+ 12+ //临界值
13+ private static final int threshold = 100 ;
14+ 15+ private long start ;
16+ private long end ;
17+ 18+ public CountTaskForkJoinTest (long start , long end ) {
19+ this .start = start ;
20+ this .end = end ;
21+ }
22+ 23+ /**
24+ * ForkJoin实现,返回计算结果
25+ *
26+ * @param start 起始值
27+ * @param end 结束值
28+ * @return
29+ * @throws InterruptedException
30+ * @throws ExecutionException
31+ */
32+ private static long forkJoinTest (long start , long end ) throws InterruptedException , ExecutionException {
33+ ForkJoinPool pool = new ForkJoinPool ();
34+ CountTaskForkJoinTest task = new CountTaskForkJoinTest (start , end );
35+ 36+ Future <Long > result = pool .submit (task );
37+ return result .get ();
38+ }
39+ 40+ public static void main (String [] args ) throws InterruptedException , ExecutionException {
41+ long start = System .currentTimeMillis ();
42+ long start_index = 1 ;
43+ long end_index = 20000 ;
44+ long ret = forkJoinTest (start_index , end_index );
45+ System .out .println ("result: " + ret );
46+ long start2 = System .currentTimeMillis ();
47+ System .out .println ("执行耗时: " + (start2 - start ));
48+ long sum = 0L ;
49+ for (;start_index <= end_index ;start_index ++){
50+ sum += start_index ;
51+ try {
52+ Thread .sleep (1L );
53+ }catch (Exception e ){
54+ ;
55+ }
56+ }
57+ System .out .println (sum );
58+ System .out .println ("执行耗时: " + (System .currentTimeMillis () - start2 ));
59+ }
60+ 61+ /**
62+ * 重写compute方法,判断是否将任务进行拆分计算
63+ */
64+ @ Override
65+ protected Long compute () {
66+ long sum = 0 ;
67+ //判断是否是拆分完毕
68+ boolean canCompute = (end - start ) <= threshold ;
69+ if (canCompute ) {
70+ for (long i = start ; i <= end ; i ++) {
71+ try {
72+ Thread .sleep (1L );
73+ }catch (Exception e ){
74+ ;
75+ }
76+ sum += i ;
77+ }
78+ } else {
79+ long middle = (start + end ) / 2 ;
80+ CountTaskForkJoinTest task1 = new CountTaskForkJoinTest (start , middle );
81+ CountTaskForkJoinTest task2 = new CountTaskForkJoinTest (middle + 1 , end );
82+ 83+ task1 .fork ();
84+ task2 .fork ();
85+ 86+ long result1 = task1 .join ();
87+ long result2 = task2 .join ();
88+ sum = result1 + result2 ;
89+ }
90+ return sum ;
91+ }
92+ }
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