1、現代的計算機已經向多CPU方向發展，即使是普通的PC，甚至現在的智能手機、多核處理器已被廣泛應用。在未來，處理器的核心數將會發展的越來越多。雖然硬件上的多核CPU已經十分成熟，但是很多應用程序并未這種多核CPU做好準備，因此并不能很好地利用多核CPU的性能優勢。為了充分利用多CPU、多核CPU的性能優勢，級軟基軟件系統應該可以充分“挖掘”每個CPU的計算能力，決不能讓某個CPU處于“空閑”狀態。為此，可以考慮把一個任務拆分成多個“小任務”,把多個"小任務"放到多個處理器核心上并行執行。當多個“小任務”執行完成之后，再將這些執行結果合并起來即可。如下面的示意圖所示：第一步分割

2、任務。首先我們需要有一個fork類來把大任務分割成子任務，有可能子任務還是很大，所以還需要不停的分割，直到分割出的子任務足夠小。第二步執行任務并合并結果。分割的子任務分別放在雙端隊列里，然后幾個啟動線程分別從雙端隊列里獲取任務執行。子任務執行完的結果都統一放在一個隊列里，啟動一個線程從隊列里拿數據，然后合并這些數據。Java提供了ForkJoinPool來支持將一個任務拆分成多個“小任務”并行計算，再把多個“小任務”的結果合成總的計算結果。ForkJoinPool是ExecutorService的實現類，因此是一種特殊的線程池。ForkJoinPool提供了如下兩個常用的構造器。·

3、 public ForkJoinPool(int parallelism)：創建一個包含parallelism個并行線程的ForkJoinPool·  public ForkJoinPool() ：以Runtime.getRuntime().availableProcessors()的返回值作為parallelism來創建ForkJoinPool創建ForkJoinPool實例后，可以釣魚ForkJoinPool的submit(ForkJoinTask<T> task)或者invoke(ForkJoinTask<T> task)來執行指定任

4、務。其中ForkJoinTask代表一個可以并行、合并的任務。ForkJoinTask是一個抽象類，它有兩個抽象子類：RecursiveAction和RecursiveTask。· RecursiveTask代表有返回值的任務· RecursiveAction代表沒有返回值的任務。一、RecursiveAction下面以一個沒有返回值的大任務為例，介紹一下RecursiveAction的用法。大任務是：打印0-200的數值。小任務是：每次只能打印50個數值。java view plaincopyprint?1. import java.util.concurren

5、t.ForkJoinPool;  2. import java.util.concurrent.RecursiveAction;  3. import java.util.concurrent.TimeUnit;  4.   5. /RecursiveAction為ForkJoinTask的抽象子類，沒有返回值的任務   6. class PrintTask extends RecursiveAction   7.

6、    / 每個"小任務"最多只打印50個數   8.     private static final int MAX = 50;  9.   10.     private int start;  11.     private int

7、 end;  12.   13.     PrintTask(int start, int end)   14.         this.start = start;  15.         this.end = end;&#

8、160; 16.       17.   18.     Override  19.     protected void compute()   20.         / 當end-start的值小于MAX時候，開始打印   21.  

9、       if (end - start) < MAX)   22.             for (int i = start; i < end; i+)   23.   

10、0;             System.out.println(Thread.currentThread().getName() + "的i值:"  24.                     

11、0;   + i);  25.               26.          else   27.             / 將大任務分解成

12、兩個小任務   28.             int middle = (start + end) / 2;  29.             PrintTask left = new PrintTask(s

13、tart, middle);  30.             PrintTask right = new PrintTask(middle, end);  31.             / 并行執行兩個小任務   32. &#

14、160;           left.fork();  33.             right.fork();  34.           35.       3

15、6.   37.   38. public class ForkJoinPoolTest   39.     /* 40.      * param args 41.      * throws Exception 42.      */ 

16、 43.     public static void main(String args) throws Exception   44.         / 創建包含Runtime.getRuntime().availableProcessors()返回值作為個數的并行線程的ForkJoinPool   45.    

17、     ForkJoinPool forkJoinPool = new ForkJoinPool();  46.         / 提交可分解的PrintTask任務   47.         forkJoinPool.submit(new PrintTask(0, 200

18、);  48.         forkJoinPool.awaitTermination(2, TimeUnit.SECONDS);/阻塞當前線程直到 ForkJoinPool 中所有的任務都執行結束   49.         / 關閉線程池   50.       

19、0; forkJoinPool.shutdown();  51.       52.   53.   import java.util.concurrent.ForkJoinPool;import java.util.concurrent.RecursiveAction;import java.util.concurrent.TimeUnit;/RecursiveAction為ForkJoinTask的抽象子類，沒有返回值的任務class PrintTask ext

20、ends RecursiveAction / 每個"小任務"最多只打印50個數private static final int MAX = 50;private int start;private int end;PrintTask(int start, int end) this.start = start;this.end = end;Overrideprotected void compute() / 當end-start的值小于MAX時候，開始打印if (end - start) < MAX) for (int i = start; i < end; i

21、+) System.out.println(Thread.currentThread().getName() + "的i值:"+ i); else / 將大任務分解成兩個小任務int middle = (start + end) / 2;PrintTask left = new PrintTask(start, middle);PrintTask right = new PrintTask(middle, end);/ 并行執行兩個小任務left.fork();right.fork();public class ForkJoinPoolTest /* * param arg

22、s * throws Exception */public static void main(String args) throws Exception / 創建包含Runtime.getRuntime().availableProcessors()返回值作為個數的并行線程的ForkJoinPoolForkJoinPool forkJoinPool = new ForkJoinPool();/ 提交可分解的PrintTask任務forkJoinPool.submit(new PrintTask(0, 200);forkJoinPool.awaitTermination(2, TimeUnit.

23、SECONDS);/阻塞當前線程直到 ForkJoinPool 中所有的任務都執行結束/ 關閉線程池forkJoinPool.shutdown();運行結果如下：java view plaincopyprint?1. ForkJoinPool-1-worker-2的i值:75  2. ForkJoinPool-1-worker-2的i值:76  3. ForkJoinPool-1-worker-2的i值:77  4. ForkJoinPool-1-worker-2的i值:78  5. ForkJoinPool-1-

24、worker-2的i值:79  6. ForkJoinPool-1-worker-2的i值:80  7. ForkJoinPool-1-worker-2的i值:81  8. ForkJoinPool-1-worker-2的i值:82  9. ForkJoinPool-1-worker-2的i值:83  10. ForkJoinPool-1-worker-2的i值:84  11. ForkJoinPool-1-worker-2的i值:85  12. Fork

25、JoinPool-1-worker-2的i值:86  13. ForkJoinPool-1-worker-2的i值:87  14. ForkJoinPool-1-worker-2的i值:88  15. ForkJoinPool-1-worker-2的i值:89  16. ForkJoinPool-1-worker-2的i值:90  17. ForkJoinPool-1-worker-2的i值:91  18. ForkJoinPool-1-worker-2的i值:92 

26、; 19. ForkJoinPool-1-worker-2的i值:93  20. ForkJoinPool-1-worker-2的i值:94  21. ForkJoinPool-1-worker-2的i值:95  22. ForkJoinPool-1-worker-2的i值:96  23. ForkJoinPool-1-worker-2的i值:97  24. ForkJoinPool-1-worker-2的i值:98  25. ForkJoinPool-1-work

27、er-2的i值:99  26. ForkJoinPool-1-worker-2的i值:50  27. ForkJoinPool-1-worker-2的i值:51  28. ForkJoinPool-1-worker-2的i值:52  29. ForkJoinPool-1-worker-2的i值:53  30. ForkJoinPool-1-worker-2的i值:54  31. ForkJoinPool-1-worker-2的i值:55  32. Fork

28、JoinPool-1-worker-2的i值:56  33. ForkJoinPool-1-worker-2的i值:57  34. ForkJoinPool-1-worker-2的i值:58  35. ForkJoinPool-1-worker-2的i值:59  36. ForkJoinPool-1-worker-2的i值:60  37. ForkJoinPool-1-worker-2的i值:61  38. ForkJoinPool-1-worker-2的i值:62 

29、; 39. ForkJoinPool-1-worker-2的i值:63  40. ForkJoinPool-1-worker-2的i值:64  41. ForkJoinPool-1-worker-2的i值:65  42. ForkJoinPool-1-worker-2的i值:66  43. ForkJoinPool-1-worker-2的i值:67  44. ForkJoinPool-1-worker-2的i值:68  45. ForkJoinPool-1-work

30、er-2的i值:69  46. ForkJoinPool-1-worker-1的i值:175  47. ForkJoinPool-1-worker-1的i值:176  48. ForkJoinPool-1-worker-1的i值:177  49. ForkJoinPool-1-worker-1的i值:178  50. ForkJoinPool-1-worker-1的i值:179  51. ForkJoinPool-1-worker-1的i值:180  52

31、. ForkJoinPool-1-worker-1的i值:181  53. ForkJoinPool-1-worker-1的i值:182  54. ForkJoinPool-1-worker-1的i值:183  55. ForkJoinPool-1-worker-1的i值:184  56. ForkJoinPool-1-worker-1的i值:185  57. ForkJoinPool-1-worker-1的i值:186  58. ForkJoinPool-1-worker-

32、1的i值:187  59. ForkJoinPool-1-worker-1的i值:188  60. ForkJoinPool-1-worker-1的i值:189  61. ForkJoinPool-1-worker-1的i值:190  62. ForkJoinPool-1-worker-1的i值:191  63. ForkJoinPool-1-worker-1的i值:192  64. ForkJoinPool-1-worker-1的i值:193  65.

33、ForkJoinPool-1-worker-1的i值:194  66. ForkJoinPool-1-worker-1的i值:195  67. ForkJoinPool-1-worker-1的i值:196  68. ForkJoinPool-1-worker-1的i值:197  69. ForkJoinPool-1-worker-1的i值:198  70. ForkJoinPool-1-worker-1的i值:199  71. ForkJoinPool-1-worker-1的

34、i值:150  72. ForkJoinPool-1-worker-1的i值:151  73. ForkJoinPool-1-worker-1的i值:152  74. ForkJoinPool-1-worker-1的i值:153  75. ForkJoinPool-1-worker-1的i值:154  76. ForkJoinPool-1-worker-1的i值:155  77. ForkJoinPool-1-worker-1的i值:156  78. Fo

35、rkJoinPool-1-worker-1的i值:157  79. ForkJoinPool-1-worker-1的i值:158  80. ForkJoinPool-1-worker-1的i值:159  81. ForkJoinPool-1-worker-1的i值:160  82. ForkJoinPool-1-worker-1的i值:161  83. ForkJoinPool-1-worker-1的i值:162  84. ForkJoinPool-1-worker-1的i值

36、:163  85. ForkJoinPool-1-worker-1的i值:164  86. ForkJoinPool-1-worker-1的i值:165  87. ForkJoinPool-1-worker-1的i值:166  88. ForkJoinPool-1-worker-1的i值:167  89. ForkJoinPool-1-worker-1的i值:168  90. ForkJoinPool-1-worker-1的i值:169  91. Fork

37、JoinPool-1-worker-1的i值:170  92. ForkJoinPool-1-worker-1的i值:171  93. ForkJoinPool-1-worker-1的i值:172  94. ForkJoinPool-1-worker-1的i值:173  95. ForkJoinPool-1-worker-1的i值:174  96. ForkJoinPool-1-worker-1的i值:125  97. ForkJoinPool-1-worker-1的i值:1

38、26  98. ForkJoinPool-1-worker-1的i值:127  99. ForkJoinPool-1-worker-1的i值:128  100. ForkJoinPool-1-worker-1的i值:129  101. ForkJoinPool-1-worker-1的i值:130  102. ForkJoinPool-1-worker-1的i值:131  103. ForkJoinPool-1-worker-1的i值:132  104. F

39、orkJoinPool-1-worker-1的i值:133  105. ForkJoinPool-1-worker-1的i值:134  106. ForkJoinPool-1-worker-1的i值:135  107. ForkJoinPool-1-worker-1的i值:136  108. ForkJoinPool-1-worker-1的i值:137  109. ForkJoinPool-1-worker-1的i值:138  110. ForkJoinPool-1-work

40、er-1的i值:139  111. ForkJoinPool-1-worker-1的i值:140  112. ForkJoinPool-1-worker-1的i值:141  113. ForkJoinPool-1-worker-1的i值:142  114. ForkJoinPool-1-worker-1的i值:143  115. ForkJoinPool-1-worker-1的i值:144  116. ForkJoinPool-1-worker-1的i值:145 &

41、#160;117. ForkJoinPool-1-worker-1的i值:146  118. ForkJoinPool-1-worker-1的i值:147  119. ForkJoinPool-1-worker-1的i值:148  120. ForkJoinPool-1-worker-1的i值:149  121. ForkJoinPool-1-worker-1的i值:100  122. ForkJoinPool-1-worker-1的i值:101  123. ForkJoin

42、Pool-1-worker-1的i值:102  124. ForkJoinPool-1-worker-1的i值:103  125. ForkJoinPool-1-worker-1的i值:104  126. ForkJoinPool-1-worker-1的i值:105  127. ForkJoinPool-1-worker-1的i值:106  128. ForkJoinPool-1-worker-1的i值:107  129. ForkJoinPool-1-worker-1的i值

43、:108  130. ForkJoinPool-1-worker-1的i值:109  131. ForkJoinPool-1-worker-1的i值:110  132. ForkJoinPool-1-worker-1的i值:111  133. ForkJoinPool-1-worker-1的i值:112  134. ForkJoinPool-1-worker-1的i值:113  135. ForkJoinPool-1-worker-1的i值:114  13

44、6. ForkJoinPool-1-worker-1的i值:115  137. ForkJoinPool-1-worker-1的i值:116  138. ForkJoinPool-1-worker-1的i值:117  139. ForkJoinPool-1-worker-1的i值:118  140. ForkJoinPool-1-worker-1的i值:119  141. ForkJoinPool-1-worker-1的i值:120  142. ForkJoinPool-1-

45、worker-1的i值:121  143. ForkJoinPool-1-worker-1的i值:122  144. ForkJoinPool-1-worker-1的i值:123  145. ForkJoinPool-1-worker-1的i值:124  146. ForkJoinPool-1-worker-1的i值:25  147. ForkJoinPool-1-worker-1的i值:26  148. ForkJoinPool-1-worker-1的i值:27 

46、 149. ForkJoinPool-1-worker-1的i值:28  150. ForkJoinPool-1-worker-1的i值:29  151. ForkJoinPool-1-worker-1的i值:30  152. ForkJoinPool-1-worker-1的i值:31  153. ForkJoinPool-1-worker-1的i值:32  154. ForkJoinPool-1-worker-1的i值:33  155. ForkJoinPool-

47、1-worker-1的i值:34  156. ForkJoinPool-1-worker-1的i值:35  157. ForkJoinPool-1-worker-1的i值:36  158. ForkJoinPool-1-worker-1的i值:37  159. ForkJoinPool-1-worker-1的i值:38  160. ForkJoinPool-1-worker-1的i值:39  161. ForkJoinPool-1-worker-1的i值:40 &#

48、160;162. ForkJoinPool-1-worker-1的i值:41  163. ForkJoinPool-1-worker-1的i值:42  164. ForkJoinPool-1-worker-1的i值:43  165. ForkJoinPool-1-worker-1的i值:44  166. ForkJoinPool-1-worker-1的i值:45  167. ForkJoinPool-1-worker-1的i值:46  168. ForkJoinPool-1-

49、worker-1的i值:47  169. ForkJoinPool-1-worker-1的i值:48  170. ForkJoinPool-1-worker-1的i值:49  171. ForkJoinPool-1-worker-1的i值:0  172. ForkJoinPool-1-worker-1的i值:1  173. ForkJoinPool-1-worker-1的i值:2  174. ForkJoinPool-1-worker-1的i值:3  17

50、5. ForkJoinPool-1-worker-1的i值:4  176. ForkJoinPool-1-worker-1的i值:5  177. ForkJoinPool-1-worker-1的i值:6  178. ForkJoinPool-1-worker-1的i值:7  179. ForkJoinPool-1-worker-1的i值:8  180. ForkJoinPool-1-worker-1的i值:9  181. ForkJoinPool-1-worker-1的i值:

51、10  182. ForkJoinPool-1-worker-1的i值:11  183. ForkJoinPool-1-worker-1的i值:12  184. ForkJoinPool-1-worker-1的i值:13  185. ForkJoinPool-1-worker-1的i值:14  186. ForkJoinPool-1-worker-1的i值:15  187. ForkJoinPool-1-worker-1的i值:16  188. ForkJ

52、oinPool-1-worker-1的i值:17  189. ForkJoinPool-1-worker-1的i值:18  190. ForkJoinPool-1-worker-1的i值:19  191. ForkJoinPool-1-worker-1的i值:20  192. ForkJoinPool-1-worker-1的i值:21  193. ForkJoinPool-1-worker-1的i值:22  194. ForkJoinPool-1-worker-1的i值:23

53、  195. ForkJoinPool-1-worker-1的i值:24  196. ForkJoinPool-1-worker-2的i值:70  197. ForkJoinPool-1-worker-2的i值:71  198. ForkJoinPool-1-worker-2的i值:72  199. ForkJoinPool-1-worker-2的i值:73  200. ForkJoinPool-1-worker-2的i值:74  ForkJoinPool

54、-1-worker-2的i值:75ForkJoinPool-1-worker-2的i值:76ForkJoinPool-1-worker-2的i值:77ForkJoinPool-1-worker-2的i值:78ForkJoinPool-1-worker-2的i值:79ForkJoinPool-1-worker-2的i值:80ForkJoinPool-1-worker-2的i值:81ForkJoinPool-1-worker-2的i值:82ForkJoinPool-1-worker-2的i值:83ForkJoinPool-1-worker-2的i值:84ForkJoinPool-1-worker-

55、2的i值:85ForkJoinPool-1-worker-2的i值:86ForkJoinPool-1-worker-2的i值:87ForkJoinPool-1-worker-2的i值:88ForkJoinPool-1-worker-2的i值:89ForkJoinPool-1-worker-2的i值:90ForkJoinPool-1-worker-2的i值:91ForkJoinPool-1-worker-2的i值:92ForkJoinPool-1-worker-2的i值:93ForkJoinPool-1-worker-2的i值:94ForkJoinPool-1-worker-2的i值:95For

56、kJoinPool-1-worker-2的i值:96ForkJoinPool-1-worker-2的i值:97ForkJoinPool-1-worker-2的i值:98ForkJoinPool-1-worker-2的i值:99ForkJoinPool-1-worker-2的i值:50ForkJoinPool-1-worker-2的i值:51ForkJoinPool-1-worker-2的i值:52ForkJoinPool-1-worker-2的i值:53ForkJoinPool-1-worker-2的i值:54ForkJoinPool-1-worker-2的i值:55ForkJoinPool-

57、1-worker-2的i值:56ForkJoinPool-1-worker-2的i值:57ForkJoinPool-1-worker-2的i值:58ForkJoinPool-1-worker-2的i值:59ForkJoinPool-1-worker-2的i值:60ForkJoinPool-1-worker-2的i值:61ForkJoinPool-1-worker-2的i值:62ForkJoinPool-1-worker-2的i值:63ForkJoinPool-1-worker-2的i值:64ForkJoinPool-1-worker-2的i值:65ForkJoinPool-1-worker-2

58、的i值:66ForkJoinPool-1-worker-2的i值:67ForkJoinPool-1-worker-2的i值:68ForkJoinPool-1-worker-2的i值:69ForkJoinPool-1-worker-1的i值:175ForkJoinPool-1-worker-1的i值:176ForkJoinPool-1-worker-1的i值:177ForkJoinPool-1-worker-1的i值:178ForkJoinPool-1-worker-1的i值:179ForkJoinPool-1-worker-1的i值:180ForkJoinPool-1-worker-1的i值:

59、181ForkJoinPool-1-worker-1的i值:182ForkJoinPool-1-worker-1的i值:183ForkJoinPool-1-worker-1的i值:184ForkJoinPool-1-worker-1的i值:185ForkJoinPool-1-worker-1的i值:186ForkJoinPool-1-worker-1的i值:187ForkJoinPool-1-worker-1的i值:188ForkJoinPool-1-worker-1的i值:189ForkJoinPool-1-worker-1的i值:190ForkJoinPool-1-worker-1的i值:

60、191ForkJoinPool-1-worker-1的i值:192ForkJoinPool-1-worker-1的i值:193ForkJoinPool-1-worker-1的i值:194ForkJoinPool-1-worker-1的i值:195ForkJoinPool-1-worker-1的i值:196ForkJoinPool-1-worker-1的i值:197ForkJoinPool-1-worker-1的i值:198ForkJoinPool-1-worker-1的i值:199ForkJoinPool-1-worker-1的i值:150ForkJoinPool-1-worker-1的i值:

61、151ForkJoinPool-1-worker-1的i值:152ForkJoinPool-1-worker-1的i值:153ForkJoinPool-1-worker-1的i值:154ForkJoinPool-1-worker-1的i值:155ForkJoinPool-1-worker-1的i值:156ForkJoinPool-1-worker-1的i值:157ForkJoinPool-1-worker-1的i值:158ForkJoinPool-1-worker-1的i值:159ForkJoinPool-1-worker-1的i值:160ForkJoinPool-1-worker-1的i值:

62、161ForkJoinPool-1-worker-1的i值:162ForkJoinPool-1-worker-1的i值:163ForkJoinPool-1-worker-1的i值:164ForkJoinPool-1-worker-1的i值:165ForkJoinPool-1-worker-1的i值:166ForkJoinPool-1-worker-1的i值:167ForkJoinPool-1-worker-1的i值:168ForkJoinPool-1-worker-1的i值:169ForkJoinPool-1-worker-1的i值:170ForkJoinPool-1-worker-1的i值:

63、171ForkJoinPool-1-worker-1的i值:172ForkJoinPool-1-worker-1的i值:173ForkJoinPool-1-worker-1的i值:174ForkJoinPool-1-worker-1的i值:125ForkJoinPool-1-worker-1的i值:126ForkJoinPool-1-worker-1的i值:127ForkJoinPool-1-worker-1的i值:128ForkJoinPool-1-worker-1的i值:129ForkJoinPool-1-worker-1的i值:130ForkJoinPool-1-worker-1的i值:

64、131ForkJoinPool-1-worker-1的i值:132ForkJoinPool-1-worker-1的i值:133ForkJoinPool-1-worker-1的i值:134ForkJoinPool-1-worker-1的i值:135ForkJoinPool-1-worker-1的i值:136ForkJoinPool-1-worker-1的i值:137ForkJoinPool-1-worker-1的i值:138ForkJoinPool-1-worker-1的i值:139ForkJoinPool-1-worker-1的i值:140ForkJoinPool-1-worker-1的i值:

65、141ForkJoinPool-1-worker-1的i值:142ForkJoinPool-1-worker-1的i值:143ForkJoinPool-1-worker-1的i值:144ForkJoinPool-1-worker-1的i值:145ForkJoinPool-1-worker-1的i值:146ForkJoinPool-1-worker-1的i值:147ForkJoinPool-1-worker-1的i值:148ForkJoinPool-1-worker-1的i值:149ForkJoinPool-1-worker-1的i值:100ForkJoinPool-1-worker-1的i值:

66、101ForkJoinPool-1-worker-1的i值:102ForkJoinPool-1-worker-1的i值:103ForkJoinPool-1-worker-1的i值:104ForkJoinPool-1-worker-1的i值:105ForkJoinPool-1-worker-1的i值:106ForkJoinPool-1-worker-1的i值:107ForkJoinPool-1-worker-1的i值:108ForkJoinPool-1-worker-1的i值:109ForkJoinPool-1-worker-1的i值:110ForkJoinPool-1-worker-1的i值:

67、111ForkJoinPool-1-worker-1的i值:112ForkJoinPool-1-worker-1的i值:113ForkJoinPool-1-worker-1的i值:114ForkJoinPool-1-worker-1的i值:115ForkJoinPool-1-worker-1的i值:116ForkJoinPool-1-worker-1的i值:117ForkJoinPool-1-worker-1的i值:118ForkJoinPool-1-worker-1的i值:119ForkJoinPool-1-worker-1的i值:120ForkJoinPool-1-worker-1的i值:

68、121ForkJoinPool-1-worker-1的i值:122ForkJoinPool-1-worker-1的i值:123ForkJoinPool-1-worker-1的i值:124ForkJoinPool-1-worker-1的i值:25ForkJoinPool-1-worker-1的i值:26ForkJoinPool-1-worker-1的i值:27ForkJoinPool-1-worker-1的i值:28ForkJoinPool-1-worker-1的i值:29ForkJoinPool-1-worker-1的i值:30ForkJoinPool-1-worker-1的i值:31Fork

69、JoinPool-1-worker-1的i值:32ForkJoinPool-1-worker-1的i值:33ForkJoinPool-1-worker-1的i值:34ForkJoinPool-1-worker-1的i值:35ForkJoinPool-1-worker-1的i值:36ForkJoinPool-1-worker-1的i值:37ForkJoinPool-1-worker-1的i值:38ForkJoinPool-1-worker-1的i值:39ForkJoinPool-1-worker-1的i值:40ForkJoinPool-1-worker-1的i值:41ForkJoinPool-1

70、-worker-1的i值:42ForkJoinPool-1-worker-1的i值:43ForkJoinPool-1-worker-1的i值:44ForkJoinPool-1-worker-1的i值:45ForkJoinPool-1-worker-1的i值:46ForkJoinPool-1-worker-1的i值:47ForkJoinPool-1-worker-1的i值:48ForkJoinPool-1-worker-1的i值:49ForkJoinPool-1-worker-1的i值:0ForkJoinPool-1-worker-1的i值:1ForkJoinPool-1-worker-1的i值

71、:2ForkJoinPool-1-worker-1的i值:3ForkJoinPool-1-worker-1的i值:4ForkJoinPool-1-worker-1的i值:5ForkJoinPool-1-worker-1的i值:6ForkJoinPool-1-worker-1的i值:7ForkJoinPool-1-worker-1的i值:8ForkJoinPool-1-worker-1的i值:9ForkJoinPool-1-worker-1的i值:10ForkJoinPool-1-worker-1的i值:11ForkJoinPool-1-worker-1的i值:12ForkJoinPool-1-

72、worker-1的i值:13ForkJoinPool-1-worker-1的i值:14ForkJoinPool-1-worker-1的i值:15ForkJoinPool-1-worker-1的i值:16ForkJoinPool-1-worker-1的i值:17ForkJoinPool-1-worker-1的i值:18ForkJoinPool-1-worker-1的i值:19ForkJoinPool-1-worker-1的i值:20ForkJoinPool-1-worker-1的i值:21ForkJoinPool-1-worker-1的i值:22ForkJoinPool-1-worker-1的i

73、值:23ForkJoinPool-1-worker-1的i值:24ForkJoinPool-1-worker-2的i值:70ForkJoinPool-1-worker-2的i值:71ForkJoinPool-1-worker-2的i值:72ForkJoinPool-1-worker-2的i值:73ForkJoinPool-1-worker-2的i值:74從上面結果來看，ForkJoinPool啟動了兩個線程來執行這個打印任務，這是因為筆者的計算機的CPU是雙核的。不僅如此，讀者可以看到程序雖然打印了0-199這兩百個數字，但是并不是連續打印的，這是因為程序將這個打印任務進行了分解，分解后的任務

74、會并行執行，所以不會按順序從0打印 到199。二、RecursiveTask下面以一個有返回值的大任務為例，介紹一下RecursiveTask的用法。大任務是：計算隨機的100個數字的和。小任務是：每次只能20個數值的和。java view plaincopyprint?1. import java.util.Random;  2. import java.util.concurrent.ForkJoinPool;  3. import java.util.concurrent.Future;  4. i

75、mport java.util.concurrent.RecursiveTask;  5.   6. /RecursiveTask為ForkJoinTask的抽象子類，有返回值的任務   7. class SumTask extends RecursiveTask<Integer>   8.     / 每個"小任務"最多只打印50個數   9.  

76、60;  private static final int MAX = 20;  10.     private int arr;  11.     private int start;  12.     private int end;  13.   14.     SumTask(int arr, int start, int end)   15.