{"id":4063,"date":"2022-12-05T13:44:54","date_gmt":"2022-12-05T05:44:54","guid":{"rendered":"https:\/\/www.zeroheart.xyz\/wordpress\/?p=4063"},"modified":"2022-12-05T14:39:37","modified_gmt":"2022-12-05T06:39:37","slug":"copyonwritearraylist%e7%9c%9f%e7%9a%84%e7%ba%bf%e7%a8%8b%e5%ae%89%e5%85%a8%e5%90%97","status":"publish","type":"post","link":"https:\/\/www.zeroheart.xyz\/wordpress\/?p=4063","title":{"rendered":"CopyOnWriteArrayList\u771f\u7684\u7ebf\u7a0b\u5b89\u5168\u5417?"},"content":{"rendered":"\n

\u539f\u6587\uff1aCopyOnWriteArrayList\u771f\u7684\u7ebf\u7a0b\u5b89\u5168\u5417? – \u6398\u91d1 (juejin.cn)<\/a><\/p>\n\n\n\n

\"CopyOnWriteArrayList\u771f\u7684\u7ebf\u7a0b\u5b89\u5168\u5417?\"\/<\/figure>\n\n\n\n
\n

\u524d\u51e0\u5929\u5237\u535a\u5ba2\u65f6\uff0c\u65e0\u610f\u4e2d\u770b\u5230\u4e00\u7bc7\u540d\u4e3a\u300aCopyOnWriteArrayList\u771f\u7684\u5b8c\u5168\u7ebf\u7a0b\u5b89\u5168\u5417\u300b\u535a\u5ba2\u3002\u5fc3\u4e2d\u4e0d\u7981\u6cdb\u8d77\u7591\u95ee\uff0c\u5b83\u5c31\u662f\u7ebf\u7a0b\u5b89\u5168\u7684\u554a\uff0c\u96be\u9053\u8fd8\u6709\u5565\u7279\u6b8a\u60c5\u51b5\uff1f<\/p>\n<\/blockquote>\n\n\n\n

\u6211\u4eec\u77e5\u9053CopyOnWrite<\/code>\u7684\u6838\u5fc3\u601d\u60f3\u6b63\u5982\u5176\u540d\uff1a\u5199\u65f6\u590d\u5236<\/code>\u3002\u5728\u5bf9\u6570\u636e\u6709\u4fee\u6539\u64cd\u4f5c\u65f6\uff0c\u5148\u590d\u5236\u518d\u64cd\u4f5c\uff0c\u6700\u540e\u66ff\u6362\u539f\u6570\u7ec4\u3002\u5728\u8fd9\u4e9b\u64cd\u4f5c\u65f6\uff0c\u662f\u6709\u52a0\u9501\u7684\u4e86\u3002<\/p>\n\n\n\n

1 \u95ee\u9898\u590d\u73b0<\/h3>\n\n\n\n

\u8fd9\u7bc7\u535a\u6587\u4e2d\u4e3b\u8981\u63d0\u5230\u6570\u7ec4\u8d8a\u754c<\/code>\u5f02\u5e38\u3002\u573a\u666f\u4e3a\uff1a\u5047\u8bbe\u73b0\u5728\u6709\u4e00\u4e2a\u5df2\u5b58\u5728\u7684\u5217\u8868\uff0c\u7ebf\u7a0b1\u5c1d\u8bd5\u53bb\u67e5\u8be2\u5217\u8868\u6700\u540e\u4e00\u4e2a\u5143\u7d20\uff0c\u800c\u6b64\u65f6\u7ebf\u7a0b2\u8981\u53bb\u5220\u9664\u5217\u8868\u6700\u540e\u4e00\u4e2a\u5143\u7d20\u3002\u6b64\u65f6\u7ebf\u7a0b1\u7531\u4e8e\u6700\u5f00\u59cb\u8bfb\u53d6\u7684size()=n\uff0c\u5728\u7ebf\u7a0b2\u5220\u9664\u540esize()=n-1\uff0c\u518d\u62ff\u539fIndex\u65b9\u5f0f\u65f6\uff0c\u4fbf\u89e6\u53d1ArrayIndexOutOfBoundsException<\/code>\u5f02\u5e38\u3002<\/p>\n\n\n\n

\u5176\u5b9e\u8bfb\u5230\u8fd9\u91cc\uff0c\u6211\u4eec\u5c31\u5df2\u7ecf\u77e5\u9053\u4e86\u95ee\u9898\u6240\u5728\u3002\u5728\u8bfb\u53d6\u5217\u8868\u5927\u5c0f<\/code>\u548c\u6839\u636e\u7d22\u5f15\u8bbf\u95ee<\/code>\u4e24\u4e2a\u65f6\u95f4\u70b9\uff0c\u5217\u8868\u6570\u636e\u5df2\u7ecf\u53d1\u751f\u4e86\u6539\u53d8\u3002\u8fd9\u79cd\u5f02\u5e38\u7406\u8bba\u4e0a\u5c5e\u4e8e\u53ef\u9884\u77e5\u7684\u5f02\u5e38\u3002<\/p>\n\n\n\n

\u8bf7\u770b\u4e0b\u9762\u7684\u4ee3\u7801\uff0c\u5e76\u601d\u8003\u4e0b\u5e76\u53d1\u6267\u884c\u4f1a\u6709\u95ee\u9898\u5417<\/p>\n\n\n\n

CopyOnWriteArrayList<String> cowList = new<\/strong> CopyOnWriteArrayList<\/strong><>(l);\n\nwhile<\/strong> (true) {\n    if<\/strong> (!cowList.isEmpty()) {\n        cowList.remove(0);\n    } else<\/strong> {\n        return<\/strong>;\n    }\n}\n <\/code><\/pre>\n\n\n\n
\u6211\u4eec\u4e0d\u59a8\u6765\u8bd5\u4e0b\u3002<\/p>\n\n\n\n
\/**\n * @author lpe234\n * @date 2022\/12\/03\n *\/<\/em>\n@Slf4j<\/strong>\npublic<\/strong> class<\/strong> CowalTest<\/strong> {\n    public<\/strong> static<\/strong> void main<\/strong>(String[] args) {\n        List<\/strong><String<\/strong>> l = new<\/strong> ArrayList<\/strong><>();\n        for<\/strong> (int i = 0; i < 100; i++) {\n            l.add<\/strong>(String<\/strong>.valueOf<\/strong>(i));\n        }\n\n        CopyOnWriteArrayList<\/strong><String<\/strong>> cowList = new<\/strong> CopyOnWriteArrayList<\/strong><>(l);\n\n        final Runnable<\/strong> rab = () -> {\n            while<\/strong> (true) {\n                if<\/strong> (!cowList.isEmpty<\/strong>()) {\n                    cowList.remove<\/strong>(0);\n                } else<\/strong> {\n                    return<\/strong>;\n                }\n            }\n        };\n\n        new<\/strong> Thread<\/strong>(rab).start<\/strong>();\n        new<\/strong> Thread<\/strong>(rab).start<\/strong>();\n    }\n}\n <\/code><\/pre>\n\n\n\n
\u7a0b\u5e8f\u6267\u884c\u7ed3\u679c\u5982\u4e0b\uff1a<\/p>\n\n\n\n
Exception in<\/strong> thread \"Thread-1\" java.lang.ArrayIndexOutOfBoundsException: Index 0 out of bounds for<\/strong> length 0\n\tat java.base\/java.util.concurrent.CopyOnWriteArrayList.elementAt(CopyOnWriteArrayList.java:386)\n\tat java.base\/java.util.concurrent.CopyOnWriteArrayList.remove(CopyOnWriteArrayList.java:478)\n\tat com.example.other.CowalTest.lambda$main$0(CowalTest.java:25)\n\tat java.base\/java.lang.Thread.run(Thread.java:834)\n <\/code><\/pre>\n\n\n\n
\u539f\u56e0\u5c31\u5728\u4e8ecowList.isEmpty()<\/code>\u548ccowList.remove(0)<\/code>\u4e3a\u4e24\u4e2a\u64cd\u4f5c\u3002\u5728\u8fd9\u4e24\u4e2a\u64cd\u4f5c\u4e4b\u95f4\uff0c\u5e76\u6ca1\u6709\u4ec0\u4e48\u673a\u5236\u6765\u4fdd\u8bc1cowList<\/code>\u4e0d\u4f1a\u6539\u53d8\u3002\u6240\u4ee5\u51fa\u73b0\u5f02\u5e38\uff0c\u662f\u53ef\u9884\u89c1\u7684\u3002<\/p>\n\n\n\n
2 \u6e90\u7801\u5206\u6790<\/h3>\n\n\n\n
\u6838\u5fc3\u5c5e\u6027\u53caget\/set\u65b9\u6cd5\u3002<\/p>\n\n\n\n
public<\/strong> class<\/strong> CopyOnWriteArrayList<\/strong><E>\n    implements<\/strong> List<\/strong><E>, RandomAccess, Cloneable, java.io.Serializable {\n    private<\/strong> static<\/strong> final<\/strong> long<\/strong> serialVersionUID = 8673264195747942595L;\n\n    \/** \u6240\u6709\u6d89\u53ca\u5230array\u53d8\u66f4\u64cd\u4f5c\u7684\u9501\u3002(\u5728\u5185\u7f6e\u9501\u548cReentrantLock\u90fd\u53ef\u4f7f\u7528\u65f6\uff0c\u6211\u4eec\u66f4\u503e\u5411\u4e8e\u5185\u7f6e\u9501) *\/<\/em>\n    final<\/strong> transient<\/strong> Object<\/strong> lock = new<\/strong> Object<\/strong>();\n\n    \/** \u8fd9\u4e2a\u6570\u7ec4\u7684\u6240\u6709\u8bbf\u95ee\uff0c\u53ea\u4f1a\u901a\u8fc7getArray\/setArray\u6765\u8fdb\u884c\u3002 *\/<\/em>\n    private<\/strong> transient<\/strong> volatile<\/strong> Object[] array;\n\n    \/**\n     * Gets the array.  Non-private so as to also be accessible\n     * from CopyOnWriteArraySet class.\n     *\/<\/em>\n    final<\/strong> Object[] getArray() {\n        return<\/strong> array;\n    }\n\n    \/**\n     * Sets the array.\n     *\/<\/em>\n    final<\/strong> void<\/strong> setArray<\/strong>(Object[] a) {\n        array = a;\n    } <\/code><\/pre>\n\n\n\n
\u53ef\u89c1\u5b9e\u73b0\u5176\u5b9e\u5f88\u7b80\u5355\u3002\u5185\u90e8\u4f7f\u7528Object[] array<\/code>\u6765\u627f\u8f7d\u6570\u636e\u3002\u4f7f\u7528volatile<\/code>\u6765\u4fdd\u8bc1\u591a\u7ebf\u7a0b\u4e0b\u6570\u7ec4\u7684\u53ef\u89c1\u6027\u3002<\/p>\n\n\n\n
\u518d\u770b\u4e0bisEmpty<\/code>\u548cremove<\/code>\u65b9\u6cd5\u3002<\/p>\n\n\n\n
public int size() {\n    return getArray().length;<\/em>\n}\n\npublic boolean isEmpty() {\n    return size() == 0;<\/em>\n}\n\npublic E remove(int index) {\n    synchronized (lock) {\n        Object[]<\/strong> es = getArray();<\/em>\n        int len = es.length;<\/em>\n        E oldValue = elementAt(es, index);<\/em>\n        int numMoved = len - index - 1;<\/em>\n        Object[]<\/strong> newElements;<\/em>\n        if (numMoved == 0)\n            newElements = Arrays.copyOf(es, len - 1);<\/em>\n        else {\n            newElements = new Object[len - 1];<\/em>\n            System.arraycopy(es, 0, newElements, 0, index);<\/em>\n            System.arraycopy(es, index + 1, newElements, index,\n                             numMoved);<\/em>\n        }\n        setArray(newElements);<\/em>\n        return oldValue;<\/em>\n    }\n}\n\u590d\u5236\u4ee3\u7801<\/code><\/pre>\n\n\n\n
\u53ef\u4ee5\u5f88\u6e05\u6670\u7684\u770b\u5230\uff0c\u5728\u8fd9\u4fe9\u65b9\u6cd5\u4e2d\uff0c\u5747\u6709getArray()<\/code>\u8c03\u7528\u3002\u5982\u679c\u4e2d\u95f4\u51fa\u73b0\u5176\u4ed6\u7ebf\u7a0b\u4fee\u6539\u6570\u636e\uff0c\u8fd9\u4fe9\u6570\u636e\u5fc5\u7136\u4e0d\u4e00\u81f4\u3002\u5728\u770b\u4e00\u4e2aadd(E e)<\/code>\u65b9\u6cd5\u3002<\/p>\n\n\n\n
public<\/strong> boolean<\/strong> add<\/strong>(E e) {\n    synchronized<\/strong> (lock) {\n        Object[] es = getArray();\n        int<\/strong> len = es.length;\n        es = Arrays.copyOf(es, len + 1);\n        es[len] = e;\n        setArray(es);\n        return<\/strong> true;\n    }\n} <\/code><\/pre>\n\n\n\n
\u6b64\u65f6\u6211\u4eec\u53ef\u4ee5\u5f88\u6e05\u6670\u7684\u770b\u6e05\u4ed6\u7684\u7f16\u7a0b\u903b\u8f91\u3002<\/p>\n\n\n\n
    \n
  • \u51e1\u662f\u5bf9\u6570\u7ec4\u6709\u4fee\u6539\u7684\u64cd\u4f5c\uff0c\u5148\u83b7\u53d6\u9501\u3002<\/li>\n\n\n\n
  • \u901a\u8fc7getArray()<\/code>\u83b7\u53d6\u6570\u636e\u3002\u524d\u9762\u5df2\u52a0\u9501\uff0c\u4e3a\u6700\u65b0\u6570\u636e\uff0c\u5728\u91ca\u653e\u9501\u524d\u4e0d\u4f1a\u6709\u5176\u4ed6\u7ebf\u7a0b\u4fee\u6539\u3002<\/li>\n\n\n\n
  • \u5bf9\u6570\u636e\u8fdb\u884c\u76f8\u5173\u4fee\u6539\u64cd\u4f5c\uff0cArrays.copyOf<\/code>\u662f\u91cd\u70b9\u3002<\/li>\n\n\n\n
  • \u901a\u8fc7setArray(es)<\/code>\u5c06\u4fee\u6539\u540e\u7684\u6570\u636e\u8d4b\u503c\u7ed9\u539f\u6570\u7ec4\u3002<\/li>\n\n\n\n
  • \u91ca\u653e\u9501\u3002<\/li>\n<\/ul>\n\n\n\n
    3 \u601d\u8003<\/h3>\n\n\n\n
    3.1 \u901a\u8fc7\u672c\u4f8b\u6211\u4eec\u80fd\u5b66\u5230\u4ec0\u4e48<\/h4>\n\n\n\n
      \n
    • \u7c7b\u4f3cCopyOnWriteArrayList<\/code>\u8fd9\u79cd\u5e76\u53d1\u5b89\u5168\u7684\u7c7b\uff0c\u5982\u679c\u4e0d\u5408\u7406(\u4e0d\u89c4\u8303\u7684\u3001\u9519\u8bef\u7684)\u7684\u4f7f\u7528\uff0c\u4e5f\u4f1a\u5bfc\u81f4\u5e76\u53d1\u5b89\u5168\u95ee\u9898<\/li>\n\n\n\n
    • \u9762\u5bf9\u4e8b\u7269\uff0c\u8981\u77e5\u5176\u7136\u77e5\u5176\u6240\u4ee5\u7136\u3002\u53ea\u6709\u4e86\u89e3\u5185\u90e8\u539f\u7406\uff0c\u624d\u80fd\u66f4\u597d\u7684\u53bb\u4f7f\u7528\u5b83\u3002<\/li>\n\n\n\n
    • \u5728CopyOnWriteArrayList<\/code>\u4ee3\u7801\u4e2d\u53ef\u4ee5\u770b\u5230\uff0c\u5f53\u9047\u5230\u4fee\u6539\u64cd\u4f5c\u65f6\uff0c\u57fa\u672c\u90fd\u79bb\u4e0d\u5f00Arrays.copyOf<\/code>\uff0c\u8fd9\u79cd\u62f7\u8d1d\u4f1a\u5360\u7528\u989d\u5916\u4e00\u500d\u7684\u5185\u5b58\u7a7a\u95f4\u3002\u5982\u679c\u6709\u5927\u91cf\u9891\u7e41\u7684\u4fee\u6539\u64cd\u4f5c\uff0c\u663e\u7136\u662f\u4e0d\u592a\u5408\u9002\u7684\u3002<\/li>\n\n\n\n
    • \u5728\u4fee\u6539\u76f8\u5173\u64cd\u4f5c\u4ee3\u7801\u903b\u8f91\u4e2d\uff0c\u53ef\u4ee5\u4f53\u4f1a\u5230\uff0c\u6574\u4f53\u662f\u6709\u90a3\u4e48\u4e00\u70b9\u70b9\u7684\u5ef6\u8fdf\u7684\u3002\u5373\u4e00\u4e2a\u7ebf\u7a0b\u4fee\u6539\u5b8c\u5e76setArray\u540e\uff0c\u53e6\u5916\u7684\u7ebf\u7a0b\u624d\u80fd\u83b7\u53d6\u5230\u6700\u65b0\u503c\u3002<\/li>\n<\/ul>\n\n\n\n
      3.2 \u5176\u4ed6\u7684\u5462<\/h4>\n\n\n\n
        \n
      • CopyOnWrite<\/code>\u662f\u4e00\u79cd\u5f88\u597d\u7684\u601d\u60f3\uff0c\u5b83\u80fd\u591f\u4f7f\u8bfb\u3001\u5199<\/code>\u64cd\u4f5c\u5e76\u53d1\u6267\u884c\u3002\u5728Redis\u7684RDB\u5feb\u7167\u751f\u6210\u65f6\uff0c\u4e5f\u4f7f\u7528\u4e86\u8be5\u601d\u60f3\u3002<\/li>\n\n\n\n
      • \u4e3a\u4ec0\u4e48\u4f1a\u6709final transient Object lock = new Object()<\/code>\u8fd9\u4e2a\u9501\uff1f\u5982\u679c\u7ec6\u5fc3\u770b\u8fc7\u6e90\u7801\u5c31\u80fd\u660e\u767d\uff0c\u5176\u5b9e\u5c31\u662f\u6700\u5927\u7a0b\u5ea6\u7684\u51cf\u5c11\u9501\u7684\u8303\u56f4(\u7c92\u5ea6)\u3002<\/li>\n<\/ul>\n\n\n\n
        public<\/strong> boolean<\/strong> addAll<\/strong>(Collection<? extends E> c) {\n    Object[] cs = (c.getClass() == CopyOnWriteArrayList.class) ?\n        ((CopyOnWriteArrayList<?>)c).getArray() : c.toArray();\n    if<\/strong> (cs.length == 0)\n        return<\/strong> false;\n    synchronized<\/strong> (lock) {\n\t\t\/\/ \u7565...<\/em>\n\t}\n} <\/code><\/pre>\n\n\n\n
        <\/p>\n","protected":false},"excerpt":{"rendered":"
        \u539f\u6587\uff1aCopyOnWriteArrayList\u771f\u7684\u7ebf\u7a0b\u5b89\u5168\u5417? – \u6398\u91d1 (juejin.cn)  […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[],"_links":{"self":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/4063"}],"collection":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4063"}],"version-history":[{"count":4,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/4063\/revisions"}],"predecessor-version":[{"id":4067,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/4063\/revisions\/4067"}],"wp:attachment":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4063"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4063"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4063"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}