{"id":1175,"date":"2016-08-18T17:40:33","date_gmt":"2016-08-18T09:40:33","guid":{"rendered":"http:\/\/www.yeetrack.com\/?p=1175"},"modified":"2016-08-18T23:06:54","modified_gmt":"2016-08-18T15:06:54","slug":"%e8%b5%b0%e8%bf%91guava%e5%9b%9b-%e5%b9%b6%e5%8f%91","status":"publish","type":"post","link":"https:\/\/www.yeetrack.com\/?p=1175","title":{"rendered":"\u8d70\u8fd1Guava(\u56db): \u5e76\u53d1"},"content":{"rendered":"
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\u5e76\u53d1\uff1a<\/h1>\n
    \n
  • Guava\u96c6\u5408\u5904\u7406\u662f\u5f88\u5f3a\u5927\u7684(\u8fd9\u4e9b\u5728jdk8\u4e2d\u90fd\u6709\u4e9b\u5f15\u5165)\uff0c\u4f46Guava\u53d1\u5149\u7684\u5730\u65b9\u662f\u5e76\u53d1<\/span>\u3002<\/span><\/li>\n<\/ul>\n

    Monitor<\/h2>\n
      \n
    • Monitor\u5b9e\u73b0\u540c\u6b65<\/span><\/li>\n<\/ul>\n
      \/**\n * \u901a\u8fc7Monitor\u7684Guard\u8fdb\u884c\u6761\u4ef6\u963b\u585e\n *\/\n\n\npublic class MonitorSample {\n\tprivate List<String> list = new ArrayList<String>();\n\tprivate static final int MAX_SIZE = 10;\n\tprivate Monitor monitor = new Monitor();\n\t\n\tprivate Monitor.Guard listBelowCapacity = new Monitor.Guard(monitor) {\n\t\t@Override\n\t\tpublic boolean isSatisfied() {\n\t\t\treturn list.size() < MAX_SIZE;\n\t\t}\n\t};\n\n\tpublic void addToList(String item) throws InterruptedException {\n\t\tmonitor.enterWhen(listBelowCapacity); \/\/Guard(\u5f62\u5982Condition)\uff0c\u4e0d\u6ee1\u8db3\u5219\u963b\u585e\uff0c\u800c\u4e14\u6211\u4eec\u5e76\u6ca1\u6709\u5728Guard\u8fdb\u884c\u4efb\u4f55\u901a\u77e5\u64cd\u4f5c\n\t\ttry {\n\t\t\tlist.add(item);\n\t\t} finally {\n\t\t\tmonitor.leave();\n\t\t}\n\t}\n}<\/code><\/pre>\n
        \n
      • Monitor<\/span>\u5c31\u50cfjava\u672c\u571f\u7684synchronized<\/span>, ReentrantLock<\/span>\u4e00\u6837\uff0c\u6bcf\u6b21\u53ea\u8fd0\u884c\u4e00\u4e2a\u7ebf\u7a0b\u5360\u7528\uff0c\u4e14\u53ef\u91cd\u5360\u7528\uff0c\u6bcf\u4e00\u6b21\u5360\u7528\u4f1a\u5bf9\u5e94\u4e00\u6b21\u9000\u51fa\u5360\u7528\u3002<\/span><\/li>\n<\/ul>\n
        Monitor\u6700\u4f73\u5b9e\u8df5\uff1a<\/h3>\n
          \n
        • \u5c31\u5982\u4e0a\u9762\uff0c\u6211\u4eec\u901a\u8fc7if\u6761\u4ef6\u6765\u5224\u65ad\u662f\u5426\u53ef\u8fdb\u5165Monitor\u4ee3\u7801\u5757\uff0c\u5e76\u518dtry\/finally\u4e2d\u91ca\u653e\uff1a<\/span><\/li>\n<\/ul>\n
          if (monitor.enterIf(guardCondition)) {\n        try {\n              doWork();\n    } finally {\n           monitor.leave();\n       }\n}<\/code><\/pre>\n
          \u5176\u4ed6\u7684Monitor\u8bbf\u95ee\u65b9\u6cd5\uff1a<\/h3>\n
          Monitor.enter \/\/\u8fdb\u5165Monitor\u5757\uff0c\u5c06\u963b\u585e\u5176\u4ed6\u7ebf\u7a0b\u77e5\u9053Monitor.leave\nMonitor.tryEnter \/\/\u5c1d\u8bd5\u8fdb\u5165Monitor\u5757\uff0ctrue\u8868\u793a\u53ef\u4ee5\u8fdb\u5165, false\u8868\u793a\u4e0d\u80fd\uff0c\u5e76\u4e14\u4e0d\u4f1a\u4e00\u76f4\u963b\u585e\nMonitor.tryEnterIf \/\/\u6839\u636e\u6761\u4ef6\u5c1d\u8bd5\u8fdb\u5165Monitor\u5757<\/code><\/pre>\n
          \u8fd9\u4e9b\u65b9\u6cd5\u90fd\u6709\u5bf9\u5e94\u7684\u9650\u65f6\u7248\u672c\u3002<\/span><\/p>\n
          ListenableFuture\u7c7b<\/h3>\n
            \n
          • jdk5\u4e4b\u540e\u6709\u4e86Future\u8fd9\u79cd\u5f02\u6b65\u6267\u884c\u7684\u7ed3\u6784<\/span><\/li>\n<\/ul>\n
            ExecutorService executor = Executors.newCachedThreadPool();\n   Future<Integer> future = executor.submit(new Callable<Integer>(){\n                                public Integer call() throws Exception{\n                                   return service.getCount();\n} });\n\/\/Retrieve the value of computation\nInteger count = future.get();<\/code><\/pre>\n
              \n
            • ListenableFuture<\/span>\u5bf9Future\u8fdb\u884c\u4e86\u6269\u5c55\uff0c\u5141\u8bb8\u6ce8\u518c\u4e00\u4e2a\u56de\u8c03\u51fd\u6570\uff0ctask\u6267\u884c\u5b8c\u540e\u81ea\u52a8\u8c03\u7528\u3002<\/span><\/li>\n<\/ul>\n
                \n
              • \u83b7\u53d6ListableFuture<\/span>\u5bf9\u8c61\u3002<\/span><\/li>\n<\/ul>\n
                \u6b63\u5982\u6211\u4eec\u83b7\u53d6Future\u5bf9\u8c61\u8981\u901a\u8fc7ExecutorService.submit(Callable)\u6765\u83b7\u53d6\u4e00\u6837\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837\u521b\u5efaListenableFuture\u5bf9\u8c61\uff1a<\/p>\n
                executorService = MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(NUM_THREADS)); \/\/\u5305\u88c5Executors\u521b\u5efa\u7684\u7ebf\u7a0b\u6c60\nListenableFuture<String> listenableFuture = executorService.submit(new Callable<String>()...); \/\/\u83b7\u53d6ListableFuture\u5bf9\u8c61\nlistenableFuture.addListener(new Runnable() {\n      @Override\n      public void run() {\n          methodToRunOnFutureTaskCompletion();\n      }\n}, executorService); \/\/\u6ce8\u518c\u56de\u8c03\u51fd\u6570<\/code><\/pre>\n
                FutureCallback\u7c7b<\/h3>\n
                  \n
                • FutureCallback<\/span>\u5b9a\u4e49\u4e86onSuccess<\/span>\u548conFailure<\/span>\u65b9\u6cd5\uff0conSuccess\u65b9\u6cd5\u4f1a\u63a5\u6536\u4e00\u4e2aFuture\u5bf9\u8c61\uff0c\u8fd9\u6837\u6211\u4eec\u5c31\u53ef\u4ee5\u83b7\u53d6Future\u7684\u7ed3\u679c\u3002<\/span><\/li>\n<\/ul>\n
                    \n
                  • \u9996\u5148\u9700\u8981\u4e00\u4e2aFutureCallback\u5b9e\u73b0\u7c7b\u3002<\/span><\/li>\n<\/ul>\n
                    \/**\n * \u5b9a\u4e49\u4e00\u4e2aFutureCallBack\u5b9e\u73b0\u7c7b\n *\/\npublic class FutureCallbackImpl implements FutureCallback<String> {\n\tprivate StringBuilder builder = new StringBuilder();\n\n\t@Override\n\tpublic void onSuccess(String result) {\n\t\tbuilder.append(result).append(\" successfully\");\n\t}\n\n\t@Override\n\tpublic void onFailure(Throwable t) {\n\t\tbuilder.append(t.toString());\n\t}\n\n\tpublic String getCallbackResult() {\n\t\treturn builder.toString();\n\t}\n}<\/code><\/pre>\n
                    \u4f7f\u7528\u5b9e\u4f8b\uff1a<\/p>\n
                    ListeningExecutorService executorService = MoreExecutors.listeningDecorator(Executors.newCachedThreadPool());\nListenableFuture<String> futureTask = executorService.submit(new Callable<String>() { \/\/\u521b\u5efaListenaleFuture\u5bf9\u8c61\n\t\t\t\t\t@Override\n\t\t\t\t\tpublic String call() throws Exception {\n\t\t\t\t\t\treturn \"Task completed\";\n\t\t\t\t\t}\n\t\t\t\t});\nFutureCallbackImpl callback = new FutureCallbackImpl();\nFutures.addCallback(futureTask, callback); \/\/\u6dfb\u52a0\u56de\u8c03\ncallback.getCallbackResult(); \/\/\u83b7\u53d6\u7ed3\u679c<\/code><\/pre>\n
                    \u5982\u679cCallBack\u662f\u4e00\u4e2a\u8017\u65f6\u64cd\u4f5c\uff0c\u4f60\u5e94\u8be5\u9009\u62e9\u53e6\u4e00\u4e2a\u6ce8\u518cCallBack:<\/p>\n
                    Futures.addCallback(futureTask,callback,executorService); \/\/\u63d0\u4f9b\u53e6\u4e00\u4e2a\u7ebf\u7a0b\u6c60\u6765\u6267\u884c\u6027\u56de\u8c03<\/code><\/pre>\n
                    SettableFuture\u7c7b\uff1a<\/h3>\n
                    SettableFuture\u53ef\u4ee5\u7528\u6765<\/span>\u8bbe\u7f6e\u8981\u8fd4\u56de\u5f97\u503c\uff1a<\/span><\/p>\n
                     <\/p>\n
                    SettableFuture<String> sf = SettableFuture.create();\n\/\/Set a value to return\nsf.set(\"Success\");\n\/\/Or set a failure Exception\nsf.setException(someException);<\/code><\/pre>\n
                    AsyncFunction\uff1a<\/span><\/h3>\n
                      \n
                    • \u8be5\u63a5\u53e3\u4e0e\u51fd\u6570\u5f0f\u7f16\u7a0b<\/span>\u5bc6\u5207\u76f8\u5173, \u7c7b\u4f3cFunction, \u4f46apply\u65b9\u6cd5\u4f1a\u8f6c\u6362\u6210\u4e00\u4e2aListenableFuture<\/span>\u5c01\u88c5\u7684\u8303\u578b\u5bf9\u8c61\u3002<\/span><\/li>\n<\/ul>\n
                      public class AsyncFuntionSample implements AsyncFunction<Long, String> {\n\tprivate ConcurrentMap<Long, String> map = Maps.newConcurrentMap();\n\tprivate ListeningExecutorService listeningExecutorService;\n\n\t@Override\n\tpublic ListenableFuture<String> apply(final Long input) throws Exception {\n\t\tif (map.containsKey(input)) {\n\t\t\tSettableFuture<String> listenableFuture = SettableFuture.create(); \/\/\u6784\u5efa\u4e00\u4e2aSettableFuture\n\t\t\tlistenableFuture.set(map.get(input));\n\t\t\treturn listenableFuture;\n\t\t} else {\n\t\t\treturn listeningExecutorService.submit(new Callable<String>() {\n\t\t\t\t@Override\n\t\t\t\tpublic String call() throws Exception {\n\t\t\t\t\tString retrieved = \/\/compute to get the data;\n\t\t\t\t\tmap.putIfAbsent(input, retrieved);\n\t\t\t\t\treturn retrieved;\n\t\t\t\t}\n\t\t\t});\n\t\t}\n\t}\n}<\/code><\/pre>\n
                      FutureFallback\u7c7b\uff1a<\/h3>\n
                        \n
                      • Futu<\/span>reFallback<\/span>\u7528\u4e8e\u5f02\u5e38\u6062\u590d\u7684\u5907\u4efd\u3002<\/span><\/li>\n<\/ul>\n
                        \/**\n * \u5f53Future\u4efb\u52a1\u5931\u8d25\u540e, \u4f5c\u4e3a\u5907\u4efd\u7684Future\n *\/\npublic class FutureFallbackImpl implements FutureFallback<String> {\n\t@Override\n\tpublic ListenableFuture<String> create(Throwable t) throws Exception {\n\t\tif (t instanceof FileNotFoundException) {\n\t\t\tSettableFuture<String> settableFuture = SettableFuture.create();\n\t\t\tsettableFuture.set(\"Not Found\");\n\t\t\treturn settableFuture;\n\t\t}\n\t\tthrow new Exception(t);\n\t}\n}<\/code><\/pre>\n
                        Futures\u7c7b:<\/h3>\n
                          \n
                        • Fut<\/span>ures<\/span>\u7c7b\u662f\u6709\u5173Future\u5b9e\u4f8b\u7684\u4e00\u4e2a\u5de5\u5177\u7c7b\u3002<\/span><\/li>\n<\/ul>\n
                          \u5f02\u6b65\u8f6c\u6362\uff1a<\/h3>\n
                          ListenableFuture<Person> lf = Futures.transform(ListenableFuture<String> f,AsyncFunction<String,Person> af);<\/code><\/pre>\n
                          \u4f7f\u7528FutureFallbacks:<\/h3>\n
                          ListenableFuture<String> lf = Futures.withFallback(ListenableFuture<String> f,FutureFallback<String> fb);<\/code><\/pre>\n
                          RateLimiter:<\/h3>\n
                            \n
                          • RateLimi<\/span>ter<\/span>\u9650\u5236\u8bbf\u95ee\u6bcf\u79d2\u8bbf\u95ee\u8d44\u6e90\u7684\u7ebf\u7a0b\u6570\u3002\u6709\u70b9\u7c7b\u4f3c\u4fe1\u53f7\u91cfSemaphore\u3002<\/span><\/li>\n<\/ul>\n
                            RateLimiter limiter = RateLimiter.create(4.0); \/\/\u6bcf\u79d2\u4e0d\u8d85\u8fc74\u4e2a\u4efb\u52a1\u88ab\u63d0\u4ea4<\/code><\/pre>\n
                            limiter.acquire();  \/\/\u8bf7\u6c42RateLimiter, \u8d85\u8fc7permits\u4f1a\u88ab\u963b\u585e\nexecutor.submit(runnable); \/\/\u63d0\u4ea4\u4efb\u52a1<\/code><\/pre>\n
                            \u4e5f\u6709\u975e\u963b\u585e\u5f0f\u5730\u5c1d\u8bd5\uff1a<\/p>\n
                            If(limiter.tryAcquire()){ \/\/\u672a\u8bf7\u6c42\u5230limiter\u5219\u7acb\u5373\u8fd4\u56defalse\n    doSomething();\n}else{\n    doSomethingElse();\n}<\/code><\/pre>\n
                            \u6765\u6e90\uff1ahttp:\/\/my.oschina.net\/indestiny\/blog\/219368<\/p>\n<\/div>\n
                            \n
                            \u8d70\u8fd1Guava(\u4e00): \u57fa\u672c\u5de5\u5177<\/a><\/p><\/blockquote>\n