{"id":869,"date":"2014-04-03T22:56:58","date_gmt":"2014-04-03T14:56:58","guid":{"rendered":"http:\/\/coderbee.net\/?p=869"},"modified":"2014-05-03T23:04:44","modified_gmt":"2014-05-03T15:04:44","slug":"juc-cyclicbarrier-%e5%8f%af%e9%87%8d%e7%94%a8%e5%b1%8f%e9%9a%9c","status":"publish","type":"post","link":"https:\/\/coderbee.net\/index.php\/concurrent\/20140403\/869","title":{"rendered":"JUC CyclicBarrier \u53ef\u91cd\u7528\u5c4f\u969c"},"content":{"rendered":"

\u4ecb\u7ecd<\/h3>\n

CyclicBarrier \u662f\u4e00\u4e2a\u7ebf\u7a0b\u540c\u6b65\u5de5\u5177\uff0c\u7528\u4e8e\u4e00\u7ec4\u4e92\u76f8\u7b49\u5f85\u7ebf\u7a0b\u4e4b\u95f4\u7684\u534f\u8c03\uff0c\u5728\u5230\u8fbe\u67d0\u4e2a\u4e34\u754c\u70b9\u4e4b\u524d\uff0c\u8fd9\u4e9b\u7ebf\u7a0b\u5fc5\u987b\u4e92\u76f8\u7b49\u5f85\uff0c\u5728\u901a\u8fc7\u4e34\u754c\u70b9\u4e4b\u540e\uff0c\u8fd9\u4e9b\u7ebf\u7a0b\u662f\u72ec\u7acb\u7684\uff1bCountDownLatch \u662f\u8ba9\u4e00\u4e2a\u7ebf\u7a0b\u7b49\u5f85\u5176\u4ed6\u7ebf\u7a0b\u5b8c\u6210\u67d0\u4e9b\u4efb\u52a1\uff0c\u5176\u4ed6\u7ebf\u7a0b\u4e4b\u95f4\u4e00\u76f4\u662f\u72ec\u7acb\u7684\u3002<\/p>\n

CyclicBarrier \u8fd8\u5141\u8bb8\u6307\u5b9a\u4e00\u4e2a\u4efb\u52a1\uff0c\u5728\u6240\u6709\u7ebf\u7a0b\u5230\u8fbe\u4e34\u754c\u70b9\u65f6\u6267\u884c\uff0c\u7531\u6700\u540e\u5230\u8fbe\u7684\u7ebf\u7a0b\u6267\u884c\u6b64\u4efb\u52a1\u3002<\/p>\n

\u5728\u91ca\u653e\u6240\u6709\u7ebf\u7a0b\u540e\uff0cCyclicBarrier \u53ef\u4ee5\u901a\u8fc7\u91cd\u7f6e\u72b6\u6001\u6765\u91cd\u7528\uff0c\u8fd9\u4e5f\u662f Cyclic \u7684\u6765\u6e90\u3002<\/p>\n

<\/p>\n

\u4f7f\u7528\u793a\u4f8b<\/h3>\n
public class TestCyclicBarrier {\n    private static final int THREAD_NUM = 5;\n\n    public static class WorkerThread implements Runnable {\n     CyclicBarrier barrier;\n\n     public WorkerThread(CyclicBarrier b) {\n         this. barrier = b;\n     }\n\n     @Override\n     public void run() {\n         try {\n          String id = \"ID:\" + Thread.currentThread().getId();\n\n          System. out.println(id + \" before barrier\");\n\n           barrier.await(); \/\/ \u7ebf\u7a0b\u5728\u8fd9\u91cc\u7b49\u5f85\uff0c\u76f4\u5230\u6240\u6709\u7ebf\u7a0b\u90fd\u5230\u8fbebarrier\u3002\n\n          System. out.println(id + \" after barrier\");\n         } catch (Exception e) {\n          e. printStackTrace();\n         }\n     }\n    }\n\n    public static void main(String[] args) {\n     CyclicBarrier cb = new CyclicBarrier( THREAD_NUM, new Runnable() {\n         \/\/ \u5f53\u6240\u6709\u7ebf\u7a0b\u5230\u8fbebarrier\u65f6\u6267\u884c\n         @Override\n          public void run() {\n          System. out.println( \"\\nID: \" + Thread.currentThread().getId()\n              + \" doing barrier work .\\n\");\n         }\n     });\n\n     for (int i = 0; i < THREAD_NUM; i++) {\n         new Thread( new WorkerThread(cb)).start();\n     }\n    }\n}\n<\/code><\/pre>\n
\u8f93\u51fa\u7ed3\u679c\u5982\u4e0b\uff1a<\/p>\n
\nID:13 before barrier\nID:14 before barrier\nID:10 before barrier\nID:12 before barrier\nID:11 before barrier\n\nID: 14 doing barrier work .\n\nID:14 after barrier\nID:13 after barrier\nID:10 after barrier\nID:11 after barrier\nID:12 after barrier\n<\/pre>\n
\u5b9e\u73b0<\/h3>\n
\u4ee3<\/h4>\n
CyclicBarrier \u662f\u53ef\u91cd\u7528\u7684\uff0c\u90a3\u4e48\u5c31\u9700\u8981\u4e00\u5b9a\u7684\u7ed3\u6784\u6765\u7ef4\u6301\u6bcf\u6b21\u91cd\u7528\u7684\u4fe1\u606f\uff0c\u5176\u5b9a\u4e49\u4e86\u4e00\u4e2a\u5185\u90e8\u7c7bGeneration<\/code>\u6765\u63d0\u4f9b\u8fd9\u4e2a\u529f\u80fd\u3002<\/p>\n
private static class Generation {\n    boolean broken = false;\n}\n<\/code><\/pre>\n
\u5185\u90e8\u5c5e\u6027<\/h4>\n
\/\/ \u7531\u4e8e\u6d89\u53ca\u591a\u4e2a\u7ebf\u7a0b\u4e4b\u95f4\u7684\u540c\u6b65\uff0c\u5bf9\u5171\u4eab\u72b6\u6001\u8bbf\u95ee\u7684\u534f\u8c03\u5e94\u8be5\u7528\u9501\u6765\u7b80\u5316\nprivate final ReentrantLock lock = new ReentrantLock();\n\n\/\/ \u5728\u6240\u6709\u7ebf\u7a0b\u90fd\u5230\u8fbe\u4e4b\u524d\uff0c\u7528\u4e8e\u4f7f\u7ebf\u7a0b\u7b49\u5f85\u7684\u6761\u4ef6\u5bf9\u8c61\u3002\n\/\/ \u6700\u540e\u4e00\u4e2a\u7ebf\u7a0b\u5230\u8fbe\u540e\uff0c\u5524\u9192\u6240\u6709\u6b64\u5bf9\u8c61\u4e0a\u7b49\u5f85\u7684\u7ebf\u7a0b\u3002\nprivate final Condition trip = lock.newCondition();\n\n\/\/ \u53c2\u4e0e\u534f\u540c\u540c\u6b65\u7684\u7ebf\u7a0b\u6570\nprivate final int parties;\n\n\/\/ \u6240\u6709\u7ebf\u7a0b\u5230\u8fbe\u540e\u3001\u91ca\u653e\u4e4b\u524d\u6267\u884c\u7684\u547d\u4ee4\u3002\nprivate final Runnable barrierCommand;\n\n\/\/ \u5f53\u524d\u7684\u4ee3\nprivate Generation generation = new Generation();\n\n\/\/ \u7b49\u5f85\u5230\u8fbe\u7684\u7ebf\u7a0b\u6570\nprivate int count;\n<\/code><\/pre>\n
\u6838\u5fc3\u7684 wait \u903b\u8f91<\/h4>\n
CyclicBarrier \u7684 await \u65b9\u6cd5\u90fd\u4f1a\u8c03\u7528 dowait \u65b9\u6cd5\u3002<\/p>\n
\/\/ \u6838\u5fc3\u4ee3\u7801\uff0c\u8986\u76d6\u4e86\u4e0d\u540c\u7684\u7b56\u7565\nprivate int dowait(boolean timed, long nanos) throws InterruptedException,\n          BrokenBarrierException, TimeoutException {\n     \/\/ \u5148\u52a0\u9501\uff0c\u786e\u4fdd\u7ebf\u7a0b\u5b89\u5168\u6027\u3002\n     final ReentrantLock lock = this.lock;\n      lock.lock();\n     try {\n          final Generation g = generation;\n\n          if (g.broken)\n              throw new BrokenBarrierException();\n\n          if (Thread.interrupted()) {\n              breakBarrier();\n              throw new InterruptedException();\n          }\n\n           int index = --count; \/\/ \u7b49\u5f85\u7ebf\u7a0b\u6570\u51cf 1\u3002\n\n           if (index == 0) { \/\/ \u5f53\u524d\u7ebf\u7a0b\u662f\u6700\u540e\u5230\u8fbe\u7ebf\u7a0b\uff0c\u91ca\u653e\u6240\u6709\u7ebf\u7a0b\u3002\n               boolean ranAction = false;\n               try {\n                   final Runnable command = barrierCommand;\n                   if (command != null)\n                       command.run();\n\n                   ranAction = true;\n                   nextGeneration();\n                   return 0;\n              } finally {\n                   if (!ranAction)\n                        breakBarrier();\n              }\n          }\n\n           \/\/ \u975e\u7b2c\u4e00\u4e2a\u5230\u8fbe\u7684\u7ebf\u7a0b\u8981\u8fdb\u5165\u7b49\u5f85\uff0c\u653e\u5728\u5faa\u73af\u91cc\u662f\u9632\u6b62\u865a\u5047\u5524\u9192\u3002\n           \/\/ \u76f4\u5230  tripped, broken, interrupted, or timed out\n           for (;;) {\n              try {\n                   if (!timed)\n                        trip.await();\n                    else if (nanos > 0L)\n                        nanos = trip.awaitNanos(nanos);\n              } catch (InterruptedException ie) {\n                    if (g == generation && !g.broken) {\n                        breakBarrier();\n                        throw ie;\n                   } else {\n                         \/\/ We're about to finish waiting even if we had not\n                         \/\/ been interrupted, so this interrupt is deemed to\n                         \/\/ \"belong\" to subsequent execution.\n                        Thread.currentThread().interrupt();\n                   }\n              }\n\n              if (g.broken)\n                   throw new BrokenBarrierException();\n\n              if (g != generation)\n                   return index;\n\n              if (timed && nanos <= 0L) {\n                   breakBarrier();\n                   throw new TimeoutException();\n              }\n          }\n     } finally {\n          lock.unlock();\n     }\n}\n\n<\/code><\/pre>\n
\u6ce8\u610f\uff0c\u4e0a\u9762\u7684\u4ee3\u7801\u591a\u5904\u8c03\u7528\u4e86 breakBarrier  \u65b9\u6cd5\uff0c\u5b83\u7684\u6700\u4e3b\u8981\u4f5c\u7528\u5c31\u662f\u5524\u9192\u6240\u6709\u7b49\u5f85\u7ebf\u7a0b\u3002<\/p>\n
reset \u65b9\u6cd5<\/h4>\n
public void reset() {\n      final ReentrantLock lock = this.lock;\n     lock.lock();\n      try {\n          breakBarrier(); \/\/ \u6253\u7834\u5f53\u524d\u7684\u4ee3\uff0c\u4ee5\u91ca\u653e\u5f53\u524d\u8fd8\u5728\u7b49\u5f85\u7ebf\u7a0b\u3002\n          nextGeneration(); \/\/ \u5f00\u542f\u65b0\u7684\u4ee3\u3002\n     } finally {\n          lock.unlock();\n     }\n}\n\n\/\/ \u628a\u5f53\u524d\u7684\u4ee3\u6807\u4e3abroken\uff0c\u5524\u9192\u6240\u6709\u7684\u7b49\u5f85\u7ebf\u7a0b\u3002\u6301\u6709\u9501\u65f6\u8c03\u7528\u3002\nprivate void breakBarrier() {\n     generation.broken = true;\n     count = parties;\n     trip.signalAll();\n}\n<\/code><\/pre>\n\n
\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u5fae\u4fe1\u516c\u4f17\u53f7: coderbee\u7b14\u8bb0<\/strong>\uff0c\u53ef\u4ee5\u66f4\u53ca\u65f6\u56de\u590d\u4f60\u7684\u8ba8\u8bba\u3002<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
\u4ecb\u7ecd CyclicBarrier \u662f\u4e00\u4e2a\u7ebf\u7a0b\u540c\u6b65\u5de5\u5177\uff0c\u7528\u4e8e\u4e00\u7ec4\u4e92\u76f8\u7b49\u5f85\u7ebf\u7a0b\u4e4b\u95f4\u7684 … \u7ee7\u7eed\u9605\u8bfb →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[121],"tags":[160,110],"_links":{"self":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/869"}],"collection":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/comments?post=869"}],"version-history":[{"count":2,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/869\/revisions"}],"predecessor-version":[{"id":871,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/869\/revisions\/871"}],"wp:attachment":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/media?parent=869"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/categories?post=869"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/tags?post=869"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}