{"id":3934,"date":"2025-07-20T10:55:07","date_gmt":"2025-07-20T02:55:07","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=3934"},"modified":"2025-07-20T10:55:07","modified_gmt":"2025-07-20T02:55:07","slug":"aqs-%e5%a6%82%e4%bd%95%e6%94%af%e6%8c%81-condition-%e7%9a%84%e7%ad%89%e5%be%85-%e5%94%a4%e9%86%92%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/07\/20\/aqs-%e5%a6%82%e4%bd%95%e6%94%af%e6%8c%81-condition-%e7%9a%84%e7%ad%89%e5%be%85-%e5%94%a4%e9%86%92%ef%bc%9f\/","title":{"rendered":"AQS \u5982\u4f55\u652f\u6301 Condition \u7684\u7b49\u5f85\/\u5524\u9192\uff1f"},"content":{"rendered":"\n

\u5728 Java \u7684\u5e76\u53d1\u6846\u67b6\u4e2d\uff0cAQS<\/code>\uff08AbstractQueuedSynchronizer<\/code>\uff09\u901a\u8fc7\u5185\u90e8\u673a\u5236\u63d0\u4f9b\u4e86\u5bf9 Condition<\/code> \u7684\u5f3a\u5927\u652f\u6301\uff0c\u7528\u4e8e\u5b9e\u73b0\u7ebf\u7a0b\u95f4\u7684\u7b49\u5f85 \/ \u901a\u77e5<\/strong>\u534f\u8c03\u3002<\/p>\n\n\n\n

\u8fd9\u662f Java \u4e2d\u6784\u5efa \u53ef\u4e2d\u65ad\u3001\u53ef\u9650\u65f6\u3001\u53ef\u591a\u6761\u4ef6\u7b49\u5f85\u961f\u5217<\/strong>\u7684\u57fa\u7840\u3002<\/p>\n\n\n\n

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\u4e00\u3001\u4ec0\u4e48\u662f Condition\uff1f<\/h2>\n\n\n\n

Condition<\/code> \u662f Lock<\/code> \u63a5\u53e3\u7684\u4e00\u4e2a\u5b50\u7cfb\u7edf\uff0c\u7528\u6765\u66ff\u4ee3 Object.wait()\/notify()<\/code>\uff0c\u5e76\u7531 AQS<\/code> \u63d0\u4f9b\u5e95\u5c42\u652f\u6301\u3002<\/p>\n\n\n\n

Lock lock = new ReentrantLock();\nCondition condition = lock.newCondition();<\/code><\/pre>\n\n\n\n
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\u6bcf\u4e00\u4e2a Condition<\/code> \u90fd\u7ef4\u62a4\u7740\u4e00\u4e2a\u72ec\u7acb\u7684\u7b49\u5f85\u961f\u5217<\/strong>\uff0c\u7528\u4e8e\u5b58\u653e\u8c03\u7528 await()<\/code> \u540e\u963b\u585e\u7684\u7ebf\u7a0b\u8282\u70b9<\/strong>\u3002<\/p>\n<\/blockquote>\n\n\n\n
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\u4e8c\u3001AQS \u4e2d Condition \u7684\u5173\u952e\u673a\u5236<\/h2>\n\n\n\n
AQS \u4e2d\uff0cCondition \u662f\u901a\u8fc7\u4e00\u4e2a\u5d4c\u5957\u7c7b\u5b9e\u73b0\u7684\uff1a<\/h3>\n\n\n\n
public class AbstractQueuedSynchronizer {\n    public class ConditionObject implements Condition {\n        ...\n    }\n}<\/code><\/pre>\n\n\n\n
AQS \u6838\u5fc3\u961f\u5217\u7ed3\u6784\uff1a<\/h3>\n\n\n\n
\u540c\u6b65\u961f\u5217\uff08Sync Queue\uff09      \u6761\u4ef6\u961f\u5217\uff08Condition Queue\uff09\n+------+                  +------+\n| head | --> Node1       | NodeX | --> NodeY --> ...\n+------+                  +------+<\/code><\/pre>\n\n\n\n
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\u4e09\u3001\u7b49\u5f85\u4e0e\u5524\u9192\u8fc7\u7a0b\u7b80\u8ff0<\/h2>\n\n\n\n
1. await() \u7b49\u5f85\u6d41\u7a0b\uff08ConditionObject.await\uff09<\/h3>\n\n\n\n
\u8c03\u7528 condition.await()<\/code> \u4f1a\uff1a<\/p>\n\n\n\n
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  1. \u5f53\u524d\u7ebf\u7a0b\u5c01\u88c5\u6210 Node \u52a0\u5165 condition queue\uff1b<\/li>\n\n\n\n
  2. \u91ca\u653e\u9501\uff08ReentrantLock.unlock()<\/code>\uff09\uff1b<\/li>\n\n\n\n
  3. \u963b\u585e\u5f53\u524d\u7ebf\u7a0b\uff08park\uff09\uff1b<\/li>\n\n\n\n
  4. \u7b49\u5f85\u88ab signal()<\/code> \u5524\u9192\u540e\uff0c\u91cd\u65b0\u5c1d\u8bd5\u7ade\u4e89\u9501\u3002<\/li>\n<\/ol>\n\n\n\n
    \u6e90\u7801\u903b\u8f91\uff08\u7b80\u5316\uff09\uff1a<\/h4>\n\n\n\n
    public final void await() throws InterruptedException {\n    if (Thread.interrupted()) throw new InterruptedException();\n\n    Node node = addConditionWaiter();   \/\/ \u52a0\u5165 Condition \u961f\u5217\n    int savedState = fullyRelease(node); \/\/ \u91ca\u653e\u9501\n    boolean interrupted = false;\n\n    while (!isOnSyncQueue(node)) {  \/\/ \u76f4\u5230\u8fdb\u5165\u540c\u6b65\u961f\u5217\n        LockSupport.park(this);     \/\/ \u963b\u585e\u7ebf\u7a0b\n        if (Thread.interrupted()) interrupted = true;\n    }\n\n    \/\/ \u88ab\u5524\u9192\u540e\u518d\u6b21\u52a0\u5165\u540c\u6b65\u961f\u5217\u5e76\u7ade\u4e89\u9501\n    acquireQueued(node, savedState);\n    if (interrupted) throw new InterruptedException();\n}<\/code><\/pre>\n\n\n\n
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    2. signal() \u5524\u9192\u6d41\u7a0b\uff08ConditionObject.signal\uff09<\/h3>\n\n\n\n
    signal()<\/code> \u4f1a\u5c06 Condition Queue \u4e2d\u6700\u524d\u9762\u7684\u8282\u70b9<\/strong>\u8f6c\u79fb\u5230 Sync Queue<\/strong> \u4e2d\uff0c\u7b49\u5f85\u91cd\u65b0\u83b7\u53d6\u9501\u3002<\/p>\n\n\n\n
    \u6e90\u7801\u903b\u8f91\uff08\u7b80\u5316\uff09\uff1a<\/h4>\n\n\n\n
    public final void signal() {\n    if (!isHeldExclusively()) throw new IllegalMonitorStateException();\n    Node first = firstWaiter;\n    if (first != null)\n        doSignal(first); \/\/ \u8f6c\u79fb\u5230\u540c\u6b65\u961f\u5217\n}\n\nprivate void doSignal(Node first) {\n    do {\n        if ((firstWaiter = first.nextWaiter) == null)\n            lastWaiter = null;\n        first.nextWaiter = null;\n    } while (!transferForSignal(first) && (first = firstWaiter) != null);\n}<\/code><\/pre>\n\n\n\n
    transferForSignal(Node node)<\/code> \u4f1a\u5c06\u8be5 Node \u7684\u72b6\u6001\u4fee\u6539\u5e76\u6dfb\u52a0\u5230 AQS<\/code> \u7684\u540c\u6b65\u961f\u5217\uff08Sync Queue\uff09\u5c3e\u90e8\u3002<\/p>\n\n\n\n
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    \u56db\u3001\u6574\u4e2a\u6d41\u7a0b\u65f6\u5e8f\u56fe<\/h2>\n\n\n\n
    \u7ebf\u7a0bA:                  Condition Queue            Sync Queue\n\nlock.lock()\n  \u2514\u2500\u2500\u2192 condition.await()\u2500\u2500\u2510\n                          \u2193\n                    [A - Node] \u2190\u2500\u2500\u2500\u2500\u2500\u2510\n                          \u2193         \u2502\n      lock.unlock() \u2192 park          \u2502\n                                    \u2502\n\u7ebf\u7a0bB:                              \u2502\n  \u2514\u2500\u2500\u2192 lock.lock()\n  \u2514\u2500\u2500\u2192 condition.signal() \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n                          \u2193         \u2193\n                    [A - Node] \u2192 \u5165 Sync Queue\n                          \u2193\n                    unpark(Thread A)\n                          \u2193\n                    Thread A \u91cd\u65b0\u7ade\u4e89\u9501<\/code><\/pre>\n\n\n\n
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    \u4e94\u3001Condition vs Object.wait()<\/h2>\n\n\n\n
    \u7279\u6027<\/th>Condition<\/code><\/th>Object.wait()<\/code><\/th><\/tr><\/thead>
    \u591a\u6761\u4ef6\u961f\u5217<\/td>\u2705 \u652f\u6301\u591a\u4e2a Condition<\/code><\/td>\u274c \u53ea\u80fd\u6709\u4e00\u4e2a wait set<\/td><\/tr>
    \u7cbe\u7ec6\u901a\u77e5<\/td>\u2705 \u53ef\u4ee5 signal()<\/code> \u6216 signalAll()<\/code><\/td>\u274c \u53ea\u80fd notify\/notifyAll<\/code><\/td><\/tr>
    \u9501\u7c7b\u578b<\/td>\u914d\u5408 Lock<\/code>\uff08\u5982 ReentrantLock<\/code>\uff09\u4f7f\u7528<\/td>\u914d\u5408 synchronized<\/code> \u4f7f\u7528<\/td><\/tr>
    \u53ef\u4e2d\u65ad\/\u9650\u65f6<\/td>\u2705 await()<\/code> \u53ef\u8bbe\u7f6e\u8d85\u65f6\u3001\u4e2d\u65ad<\/td>\u90e8\u5206\u652f\u6301<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
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    \u516d\u3001\u5b9e\u6218\u6848\u4f8b\u793a\u4f8b<\/h2>\n\n\n\n
    class BoundedBuffer<T> {\n    private final Queue<T> queue = new LinkedList<>();\n    private final int capacity;\n\n    private final Lock lock = new ReentrantLock();\n    private final Condition notFull  = lock.newCondition();\n    private final Condition notEmpty = lock.newCondition();\n\n    public BoundedBuffer(int size) {\n        this.capacity = size;\n    }\n\n    public void put(T item) throws InterruptedException {\n        lock.lock();\n        try {\n            while (queue.size() == capacity) {\n                notFull.await();  \/\/ \u7b49\u5f85\u975e\u6ee1\n            }\n            queue.add(item);\n            notEmpty.signal();    \/\/ \u901a\u77e5\u6d88\u8d39\u8005\n        } finally {\n            lock.unlock();\n        }\n    }\n\n    public T take() throws InterruptedException {\n        lock.lock();\n        try {\n            while (queue.isEmpty()) {\n                notEmpty.await(); \/\/ \u7b49\u5f85\u975e\u7a7a\n            }\n            T item = queue.remove();\n            notFull.signal();     \/\/ \u901a\u77e5\u751f\u4ea7\u8005\n            return item;\n        } finally {\n            lock.unlock();\n        }\n    }\n}<\/code><\/pre>\n\n\n\n
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    \u4e03\u3001\u6743\u5a01\u8d44\u6599\u63a8\u8350<\/h2>\n\n\n\n