{"id":844,"date":"2014-03-11T22:23:16","date_gmt":"2014-03-11T14:23:16","guid":{"rendered":"http:\/\/coderbee.net\/?p=844"},"modified":"2014-05-03T23:04:55","modified_gmt":"2014-05-03T15:04:55","slug":"future-%e4%b8%8e-futuretask","status":"publish","type":"post","link":"https:\/\/coderbee.net\/index.php\/concurrent\/20140311\/844","title":{"rendered":"Future \u4e0e FutureTask"},"content":{"rendered":"<h2>Future<\/h2>\n<p><strong>\u6765\u81ea Java DOC \u6587\u6863<\/strong>\uff1aFuture \u8868\u793a\u5f02\u6b65\u8ba1\u7b97\u7684\u7ed3\u679c\u3002\u5b83\u63d0\u4f9b\u4e86\u68c0\u67e5\u8ba1\u7b97\u662f\u5426\u5b8c\u6210\u7684\u65b9\u6cd5\uff0c\u4ee5\u7b49\u5f85\u8ba1\u7b97\u7684\u5b8c\u6210\uff0c\u5e76\u83b7\u53d6\u8ba1\u7b97\u7684\u7ed3\u679c\u3002\u8ba1\u7b97\u5b8c\u6210\u540e\u53ea\u80fd\u4f7f\u7528 get \u65b9\u6cd5\u6765\u83b7\u53d6\u7ed3\u679c\uff0c\u5982\u6709\u5fc5\u8981\uff0c\u8ba1\u7b97\u5b8c\u6210\u524d\u53ef\u4ee5\u963b\u585e\u6b64\u65b9\u6cd5\u3002\u53d6\u6d88\u5219\u7531 cancel \u65b9\u6cd5\u6765\u6267\u884c\u3002\u8fd8\u63d0\u4f9b\u4e86\u5176\u4ed6\u65b9\u6cd5\uff0c\u4ee5\u786e\u5b9a\u4efb\u52a1\u662f\u6b63\u5e38\u5b8c\u6210\u8fd8\u662f\u88ab\u53d6\u6d88\u4e86\u3002\u4e00\u65e6\u8ba1\u7b97\u5b8c\u6210\uff0c\u5c31\u4e0d\u80fd\u518d\u53d6\u6d88\u8ba1\u7b97\u3002\u5982\u679c\u4e3a\u4e86\u53ef\u53d6\u6d88\u6027\u800c\u4f7f\u7528 Future \u4f46\u53c8\u4e0d\u63d0\u4f9b\u53ef\u7528\u7684\u7ed3\u679c\uff0c\u5219\u53ef\u4ee5\u58f0\u660e Future&lt;?> \u5f62\u5f0f\u7c7b\u578b\u3001\u5e76\u8fd4\u56de null \u4f5c\u4e3a\u5e95\u5c42\u4efb\u52a1\u7684\u7ed3\u679c\u3002<\/p>\n<p>\u4e5f\u5c31\u662f\u8bf4Future\u5177\u6709\u8fd9\u6837\u7684\u7279\u6027\uff1a<\/p>\n<ul>\n<li>\u5f02\u6b65\u6267\u884c\uff0c\u53ef\u7528 get \u65b9\u6cd5\u83b7\u53d6\u6267\u884c\u7ed3\u679c\u3002<\/li>\n<li>\u5982\u679c\u8ba1\u7b97\u8fd8\u6ca1\u5b8c\u6210\uff0cget \u65b9\u6cd5\u662f\u4f1a\u963b\u585e\u7684\uff0c\u5982\u679c\u5b8c\u6210\u4e86\uff0c\u662f\u53ef\u4ee5\u591a\u6b21\u83b7\u53d6\u5e76\u7acb\u5373\u5f97\u5230\u7ed3\u679c\u7684\u3002<\/li>\n<li>\u5982\u679c\u8ba1\u7b97\u8fd8\u6ca1\u5b8c\u6210\uff0c\u662f\u53ef\u4ee5\u53d6\u6d88\u8ba1\u7b97\u7684\u3002<\/li>\n<li>\u53ef\u4ee5\u67e5\u8be2\u8ba1\u7b97\u7684\u6267\u884c\u72b6\u6001\u3002<\/li>\n<\/ul>\n<p>\u57cb\u4e24\u4e2a\u5c0f\u95ee\u9898\u7528\u4e8e\u8bbe\u60f3\u4e0b\u600e\u4e48\u5b9e\u73b0Future\uff1a<\/p>\n<ol>\n<li>Future\u5728\u8ba1\u7b97\u5b8c\u6210\u524d\u963b\u585e get \u8bbf\u95ee\uff0c\u5b8c\u6210\u540e\u53ef\u4ee5\u81ea\u7531\u8bbf\u95ee\uff0c\u5982\u4f55\u5b9e\u73b0 get \u65b9\u6cd5\uff1f<\/li>\n<li>\u8ba1\u7b97\u7684\u53d6\u6d88\u662f\u600e\u4e48\u5b9e\u73b0\u7684\uff1f\u88ab\u53d6\u6d88\u7684\u8ba1\u7b97\u4f1a\u7ec8\u6b62\u6267\u884c\u5417\uff1f<\/li>\n<\/ol>\n<p><!--more--><\/p>\n<h2>FutureTask<\/h2>\n<p>FutureTask \u662fJUC\u91cc\u5bf9Future\u7684\u4e00\u4e2a\u5b9e\u73b0\uff0c\u8fd8\u5b9e\u73b0\u4e86 Runnable \u63a5\u53e3\uff0c\u6240\u4ee5\u53ef\u4ee5\u63d0\u4ea4\u7ed9\u7ebf\u7a0b\u6c60\u6267\u884c\u3002<\/p>\n<p>FutureTask \u53ea\u6709\u4e00\u4e2a\u81ea\u5b9a\u4e49\u7684\u540c\u6b65\u5668 Sync \u7684\u5c5e\u6027\uff0c\u6240\u6709\u7684\u65b9\u6cd5\u90fd\u662f\u59d4\u6d3e\u7ed9\u6b64\u540c\u6b65\u5668\u6765\u5b9e\u73b0\u3002\u8fd9\u4e5f\u662fJUC\u91cc\u4f7f\u7528AQS\u7684\u901a\u7528\u6a21\u5f0f\u3002<\/p>\n<p>\u4e0b\u9762\u7684\u4ee3\u7801\u662f JDK 1.7.10 \u7684\u6e90\u7801\u3002<\/p>\n<h3>FutureTask \u5b9e\u73b0<\/h3>\n<p>FutureTask\u7684\u5b9a\u4e49\uff0c\u7701\u7565\u4e86\u5f88\u591a\u4ee3\u7801\u3002<\/p>\n<pre><code class=\"java\">public class FutureTask&lt;V&gt; implements RunnableFuture&lt;V&gt; {\n    \/\/ FutureTask \u7528\u4e8e\u540c\u6b65\u63a7\u5236\n    private final Sync sync;\n\n    public boolean isCancelled() {\n        return sync.innerIsCancelled();\n    }\n\n    public boolean isDone() {\n        return sync.innerIsDone();\n    }\n\n    public V get() throws InterruptedException, ExecutionException {\n        return sync.innerGet();\n    }\n\n    \/\/ \u7701\u7565\u5176\u4ed6\u65b9\u6cd5\n}\n<\/code><\/pre>\n<h4>FutureTask \u7684\u540c\u6b65\u5668<\/h4>\n<p>\u7531\u4e8eFuture\u5728\u4efb\u52a1\u5b8c\u6210\u540e\uff0c\u53ef\u4ee5\u591a\u6b21\u81ea\u7531\u83b7\u53d6\u7ed3\u679c\uff0c\u56e0\u6b64\uff0c\u7528\u4e8e\u63a7\u5236\u540c\u6b65\u7684AQS\u4f7f\u7528\u5171\u4eab\u6a21\u5f0f\u3002<\/p>\n<p>FutureTask \u5e95\u5c42\u4efb\u52a1\u7684\u6267\u884c\u72b6\u6001\u4fdd\u5b58\u5728AQS\u7684\u72b6\u6001\u91cc\u3002AQS\u662f\u5426\u5141\u8bb8\u7ebf\u7a0b\u83b7\u53d6\uff08\u662f\u5426\u963b\u585e\uff09\u662f\u53d6\u51b3\u4e8e\u4efb\u52a1\u662f\u5426\u6267\u884c\u5b8c\u6210\uff0c\u800c\u4e0d\u662f\u5177\u4f53\u7684\u72b6\u6001\u503c\u3002<\/p>\n<pre><code class=\"java\">private final class Sync extends AbstractQueuedSynchronizer {\n    \/\/ \u5b9a\u4e49\u8868\u793a\u4efb\u52a1\u6267\u884c\u72b6\u6001\u7684\u5e38\u91cf\u3002\u7531\u4e8e\u4f7f\u7528\u4e86\u4f4d\u8fd0\u7b97\u8fdb\u884c\u5224\u65ad\uff0c\u6240\u4ee5\u72b6\u6001\u503c\u5206\u522b\u662f2\u7684\u5e42\u3002\n\n    \/\/ \u8868\u793a\u4efb\u52a1\u5df2\u7ecf\u51c6\u5907\u597d\u4e86\uff0c\u53ef\u4ee5\u6267\u884c\n    private static final int READY     = 0;\n\n    \/\/ \u8868\u793a\u4efb\u52a1\u6b63\u5728\u6267\u884c\u4e2d\n    private static final int RUNNING   = 1;\n\n    \/\/ \u8868\u793a\u4efb\u52a1\u5df2\u6267\u884c\u5b8c\u6210\n    private static final int RAN       = 2;\n\n    \/\/ \u8868\u793a\u4efb\u52a1\u5df2\u53d6\u6d88\n    private static final int CANCELLED = 4;\n\n\n    \/\/ \u5e95\u5c42\u7684\u8868\u793a\u4efb\u52a1\u7684\u53ef\u6267\u884c\u5bf9\u8c61\n    private final Callable&lt;V&gt; callable;\n\n    \/\/ \u8868\u793a\u4efb\u52a1\u6267\u884c\u7ed3\u679c\uff0c\u7528\u4e8eget\u65b9\u6cd5\u8fd4\u56de\u3002\n    private V result;\n\n    \/\/ \u8868\u793a\u4efb\u52a1\u6267\u884c\u4e2d\u7684\u5f02\u5e38\uff0c\u7528\u4e8eget\u65b9\u6cd5\u8c03\u7528\u65f6\u629b\u51fa\u3002\n    private Throwable exception;\n\n     \/*\n     * \u7528\u4e8e\u6267\u884c\u4efb\u52a1\u7684\u7ebf\u7a0b\u3002\u5728 set\/cancel \u65b9\u6cd5\u540e\u7f6e\u4e3a\u7a7a\uff0c\u8868\u793a\u7ed3\u679c\u53ef\u83b7\u53d6\u3002\n     * \u5fc5\u987b\u662f volatile\u7684\uff0c\u7528\u4e8e\u786e\u4fdd\u5b8c\u6210\u540e\uff08result\u548cexception\uff09\u7684\u53ef\u89c1\u6027\u3002\n     * \uff08\u5982\u679crunner\u4e0d\u662fvolatile\uff0c\u5219result\u548cexception\u5fc5\u987b\u90fd\u662fvolatile\u7684\uff09\n     *\/\n    private volatile Thread runner;\n\n\n     \/**\n     * \u5df2\u5b8c\u6210\u6216\u5df2\u53d6\u6d88 \u65f6\u6210\u529f\u83b7\u53d6\n     *\/\n    protected int tryAcquireShared( int ignore) {\n        return innerIsDone() ? 1 : -1;\n    }\n\n    \/**\n     * \u5728\u8bbe\u7f6e\u6700\u7ec8\u5b8c\u6210\u72b6\u6001\u540e\u8ba9AQS\u603b\u662f\u901a\u77e5\uff0c\u901a\u8fc7\u8bbe\u7f6erunner\u7ebf\u7a0b\u4e3a\u7a7a\u3002\n     * \u8fd9\u4e2a\u65b9\u6cd5\u5e76\u6ca1\u6709\u66f4\u65b0AQS\u7684state\u5c5e\u6027\uff0c\n     * \u6240\u4ee5\u53ef\u89c1\u6027\u662f\u901a\u8fc7\u5bf9volatile\u7684runner\u7684\u5199\u6765\u4fdd\u8bc1\u7684\u3002\n     *\/\n    protected boolean tryReleaseShared( int ignore) {\n        runner = null;\n        return true;\n    }\n\n\n     \/\/ \u6267\u884c\u4efb\u52a1\u7684\u65b9\u6cd5\n    void innerRun() {\n        \/\/ \u7528\u4e8e\u786e\u4fdd\u4efb\u52a1\u4e0d\u4f1a\u91cd\u590d\u6267\u884c\n        if (!compareAndSetState(READY, RUNNING))\n            return;\n\n        \/\/ \u7531\u4e8eFuture\u4e00\u822c\u662f\u5f02\u6b65\u6267\u884c\uff0c\u6240\u4ee5runner\u4e00\u822c\u662f\u7ebf\u7a0b\u6c60\u91cc\u7684\u7ebf\u7a0b\u3002\n        runner = Thread.currentThread();\n\n        \/\/ \u8bbe\u7f6e\u6267\u884c\u7ebf\u7a0b\u540e\u518d\u6b21\u68c0\u67e5\uff0c\u5728\u6267\u884c\u524d\u68c0\u67e5\u662f\u5426\u88ab\u5f02\u6b65\u53d6\u6d88\n        \/\/ \u7531\u4e8e\u524d\u9762\u7684CAS\u5df2\u628a\u72b6\u6001\u8bbe\u7f6eRUNNING\uff0c\n        if (getState() == RUNNING) { \/\/ recheck after setting thread\n            V result;\n            \/\/\n            try {\n                result = callable.call();\n            } catch (Throwable ex) {\n                \/\/ \u6355\u83b7\u4efb\u52a1\u6267\u884c\u8fc7\u7a0b\u4e2d\u629b\u51fa\u7684\u6240\u6709\u5f02\u5e38\n                setException(ex);\n                return;\n            }\n            set(result);\n        } else {\n      \/\/ \u91ca\u653e\u7b49\u5f85\u7684\u7ebf\u7a0b\n            releaseShared(0); \/\/ cancel\n        }\n    }\n\n    \/\/ \u8bbe\u7f6e\u7ed3\u679c\n    void innerSet(V v) {\n        \/\/ \u653e\u5728\u5faa\u73af\u91cc\u8fdb\u884c\u662f\u4e3a\u4e86\u5931\u8d25\u540e\u91cd\u8bd5\u3002\n        for (;;) {\n            \/\/ AQS\u521d\u59cb\u5316\u65f6\uff0c\u72b6\u6001\u503c\u9ed8\u8ba4\u662f 0\uff0c\u5bf9\u5e94\u8fd9\u91cc\u4e5f\u5c31\u662f READY \u72b6\u6001\u3002\n            int s = getState();\n\n            \/\/ \u5df2\u5b8c\u6210\u4efb\u52a1\u4e0d\u80fd\u8bbe\u7f6e\u7ed3\u679c\n            if (s == RAN)\n                return;\n\n            \/\/ \u5df2\u53d6\u6d88 \u7684\u4efb\u52a1\u4e0d\u80fd\u8bbe\u7f6e\u7ed3\u679c\n            if (s == CANCELLED) {\n                \/\/ releaseShared \u4f1a\u8bbe\u7f6erunner\u4e3a\u7a7a\uff0c\n                \/\/ \u8fd9\u662f\u8003\u8651\u5230\u4e0e\u5176\u4ed6\u7684\u53d6\u6d88\u8bf7\u6c42\u7ebf\u7a0b \u7ade\u4e89\u4e2d\u65ad runner\n                releaseShared(0);\n                return;\n            }\n\n            \/\/ \u5148\u8bbe\u7f6e\u5df2\u5b8c\u6210\uff0c\u514d\u5f97\u591a\u6b21\u8bbe\u7f6e\n            if (compareAndSetState(s, RAN)) {\n                result = v;\n                releaseShared(0); \/\/ \u6b64\u65b9\u6cd5\u4f1a\u66f4\u65b0 runner\uff0c\u4fdd\u8bc1result\u7684\u53ef\u89c1\u6027\n                done();\n                return;\n            }\n        }\n    }\n\n    \/\/ \u83b7\u53d6\u5f02\u6b65\u8ba1\u7b97\u7684\u7ed3\u679c\n    V innerGet() throws InterruptedException, ExecutionException {\n        acquireSharedInterruptibly(0);\/\/ \u83b7\u53d6\u5171\u4eab\uff0c\u5982\u679c\u6ca1\u6709\u5b8c\u6210\u5219\u4f1a\u963b\u585e\u3002\n\n        \/\/ \u68c0\u67e5\u662f\u5426\u88ab\u53d6\u6d88\n        if (getState() == CANCELLED)\n            throw new CancellationException();\n\n        \/\/ \u5f02\u6b65\u8ba1\u7b97\u8fc7\u7a0b\u4e2d\u51fa\u73b0\u5f02\u5e38\n        if (exception != null)\n            throw new ExecutionException(exception);\n\n        return result;\n    }\n\n    \/\/ \u53d6\u6d88\u6267\u884c\u4efb\u52a1\n    boolean innerCancel( boolean mayInterruptIfRunning) {\n        for (;;) {\n            int s = getState();\n\n            \/\/ \u5df2\u5b8c\u6210\u6216\u5df2\u53d6\u6d88\u7684\u4efb\u52a1\u4e0d\u80fd\u518d\u6b21\u53d6\u6d88\n            if (ranOrCancelled(s))\n                return false;\n\n            \/\/ \u4efb\u52a1\u5904\u4e8e READY \u6216 RUNNING\n            if (compareAndSetState(s, CANCELLED))\n                break;\n        }\n        \/\/ \u4efb\u52a1\u53d6\u6d88\u540e\uff0c\u4e2d\u65ad\u6267\u884c\u7ebf\u7a0b\n        if (mayInterruptIfRunning) {\n            Thread r = runner;\n            if (r != null)\n                r.interrupt();\n        }\n        releaseShared(0); \/\/ \u91ca\u653e\u7b49\u5f85\u7684\u8bbf\u95ee\u7ed3\u679c\u7684\u7ebf\u7a0b\n        done();\n        return true;\n    }\n\n    \/**\n     * \u68c0\u67e5\u4efb\u52a1\u662f\u5426\u5904\u4e8e\u5b8c\u6210\u6216\u53d6\u6d88\u72b6\u6001\n     *\/\n    private boolean ranOrCancelled( int state) {\n        return (state &amp; (RAN | CANCELLED)) != 0;\n    }\n\n     \/\/ \u5176\u4ed6\u65b9\u6cd5\u7701\u7565\n}\n<\/code><\/pre>\n<p>\u4ece innerCancel \u65b9\u6cd5\u53ef\u77e5\uff0c\u53d6\u6d88\u64cd\u4f5c\u53ea\u662f\u6539\u53d8\u4e86\u4efb\u52a1\u5bf9\u8c61\u7684\u72b6\u6001\u5e76\u53ef\u80fd\u4f1a\u4e2d\u65ad\u6267\u884c\u7ebf\u7a0b\u3002\u5982\u679c\u4efb\u52a1\u7684\u903b\u8f91\u4ee3\u7801\u6ca1\u6709\u54cd\u5e94\u4e2d\u65ad\uff0c\u5219\u4f1a\u4e00\u76f4\u5f02\u6b65\u6267\u884c\u76f4\u5230\u5b8c\u6210\uff0c\u53ea\u662f\u6700\u7ec8\u7684\u6267\u884c\u7ed3\u679c\u4e0d\u4f1a\u88ab\u901a\u8fc7get\u65b9\u6cd5\u8fd4\u56de\uff0c\u8ba1\u7b97\u8d44\u6e90\u7684\u5f00\u9500\u4ecd\u7136\u662f\u5b58\u5728\u7684\u3002<\/p>\n<p>\u603b\u7684\u6765\u8bf4\uff0cFuture \u662f\u7ebf\u7a0b\u95f4\u534f\u8c03\u7684\u4e00\u79cd\u5de5\u5177\u3002<\/p>\n<hr\/>\n<p>\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u5fae\u4fe1\u516c\u4f17\u53f7: <strong>coderbee\u7b14\u8bb0<\/strong>\uff0c\u53ef\u4ee5\u66f4\u53ca\u65f6\u56de\u590d\u4f60\u7684\u8ba8\u8bba\u3002<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"258\" height=\"258\" src=\"https:\/\/coderbee.net\/wp-content\/uploads\/2019\/01\/coderbee-note.jpg\" class=\"alignnone size-full wp-image-1707\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Future \u6765\u81ea Java DOC \u6587\u6863\uff1aFuture \u8868\u793a\u5f02\u6b65\u8ba1\u7b97\u7684\u7ed3\u679c\u3002\u5b83 &hellip; <a href=\"https:\/\/coderbee.net\/index.php\/concurrent\/20140311\/844\">\u7ee7\u7eed\u9605\u8bfb <span class=\"meta-nav\">&rarr;<\/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":[158,110],"_links":{"self":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/844"}],"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=844"}],"version-history":[{"count":2,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/844\/revisions"}],"predecessor-version":[{"id":846,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/844\/revisions\/846"}],"wp:attachment":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/media?parent=844"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/categories?post=844"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/tags?post=844"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}