{"id":1127,"date":"2020-07-21T14:58:31","date_gmt":"2020-07-21T06:58:31","guid":{"rendered":"https:\/\/www.zeroheart.xyz\/wordpress\/?p=1127"},"modified":"2020-07-21T14:58:31","modified_gmt":"2020-07-21T06:58:31","slug":"copyonwritearraylist","status":"publish","type":"post","link":"https:\/\/www.zeroheart.xyz\/wordpress\/?p=1127","title":{"rendered":"CopyOnWriteArrayList"},"content":{"rendered":"\n<p>CopyOnWrite\u6280\u672f\uff0c\u4e3b\u8981\u5904\u7406\u591a\u7ebf\u7a0b\u5e76\u53d1\u8bbf\u95ee\u7684\u95ee\u9898\u3002\u666e\u901a\u7684ArrayList\uff0c\u5982\u679c\u5e76\u53d1\u4fee\u6539\uff0c\u4f1a\u62a5\u4e00\u4e2a\u5e76\u53d1\u4fee\u6539\u5f02\u5e38ConcurrentModificationException\u3002CopyOnWrite\u5219\u901a\u8fc7\u5728\u4fee\u6539\u6570\u636e\u7684\u65f6\u5019\uff0c\u8fdb\u884c\u62f7\u8d1d\u6570\u636e\u7684\u65b9\u5f0f\uff0c\u89e3\u51b3\u4e86\u8fd9\u4e2a\u95ee\u9898\u3002\u4e0b\u9762\u6709\u662f\u4e00\u4e9b\u6e90\u7801<\/p>\n\n\n\n<p>1.\u6570\u636e\u7ed3\u6784<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\"><br>\/**\u00a0\u53ef\u91cd\u5165\u9501\u5bf9\u8c61\u00a0*\/<br>\u00a0\u00a0\u00a0\u00a0final\u00a0transient\u00a0ReentrantLock\u00a0lock\u00a0=\u00a0new\u00a0ReentrantLock();<br><br>\u00a0\u00a0\u00a0\u00a0\/**\u00a0CopyOnWriteArrayList\u5e95\u5c42\u7531\u6570\u7ec4\u5b9e\u73b0\uff0cvolatile\u4fee\u9970\u00a0*\/<br>\u00a0\u00a0\u00a0\u00a0private\u00a0transient\u00a0volatile\u00a0Object[]\u00a0array;<br><br>\u00a0\u00a0\u00a0\u00a0\/**<br>\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u5f97\u5230\u6570\u7ec4<br>\u00a0\u00a0\u00a0\u00a0\u00a0*\/<br>\u00a0\u00a0\u00a0\u00a0final\u00a0Object[]\u00a0getArray()\u00a0{<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return\u00a0array;<br>\u00a0\u00a0\u00a0\u00a0}<br><br>\u00a0\u00a0\u00a0\u00a0\/**<br>\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u8bbe\u7f6e\u6570\u7ec4<br>\u00a0\u00a0\u00a0\u00a0\u00a0*\/<br>\u00a0\u00a0\u00a0\u00a0final\u00a0void\u00a0setArray(Object[]\u00a0a)\u00a0{<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0array\u00a0=\u00a0a;<br>\u00a0\u00a0\u00a0\u00a0}<br><br>\u00a0\u00a0\u00a0\u00a0\/**<br>\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u521d\u59cb\u5316CopyOnWriteArrayList\u76f8\u5f53\u4e8e\u521d\u59cb\u5316\u6570\u7ec4<br>\u00a0\u00a0\u00a0\u00a0\u00a0*\/<br>\u00a0\u00a0\u00a0\u00a0public\u00a0CopyOnWriteArrayList()\u00a0{<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0setArray(new\u00a0Object[0]);<br>\u00a0\u00a0\u00a0\u00a0}<\/pre>\n\n\n\n<p>2.add\u65b9\u6cd5<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">public boolean add(E e) {<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0\u52a0\u9501<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0final\u00a0ReentrantLock\u00a0lock\u00a0=\u00a0this.lock;<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0lock.lock();<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0try\u00a0{<br><br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0\u5f97\u5230\u539f\u6570\u7ec4\u7684\u957f\u5ea6\u548c\u5143\u7d20<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Object[]\u00a0elements\u00a0=\u00a0getArray();<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0int\u00a0len\u00a0=\u00a0elements.length;<br><br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0\u590d\u5236\u51fa\u4e00\u4e2a\u65b0\u6570\u7ec4<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Object[]\u00a0newElements\u00a0=\u00a0Arrays.copyOf(elements,\u00a0len\u00a0+\u00a01);<br><br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0\u6dfb\u52a0\u65f6\uff0c\u5c06\u65b0\u5143\u7d20\u6dfb\u52a0\u5230\u65b0\u6570\u7ec4\u4e2d<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0newElements[len]\u00a0=\u00a0e;<br><br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0\u5c06volatile\u00a0Object[]\u00a0array\u00a0\u7684\u6307\u5411\u66ff\u6362\u6210\u65b0\u6570\u7ec4<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0setArray(newElements);<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return\u00a0true;<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}\u00a0finally\u00a0{<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0lock.unlock();<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<br>\u00a0\u00a0\u00a0\u00a0}<\/pre>\n\n\n\n<p>3.set\u65b9\u6cd5<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">public\u00a0E\u00a0set(int\u00a0index,\u00a0E\u00a0element)\u00a0{<br>\u00a0\u00a0\u00a0\u00a0final\u00a0ReentrantLock\u00a0lock\u00a0=\u00a0this.lock;<br>\u00a0\u00a0\u00a0\u00a0lock.lock();<br>\u00a0\u00a0\u00a0\u00a0try\u00a0{<br><br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0\u5f97\u5230\u539f\u6570\u7ec4\u7684\u65e7\u503c<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Object[]\u00a0elements\u00a0=\u00a0getArray();<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0E\u00a0oldValue\u00a0=\u00a0get(elements,\u00a0index);<br><br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0\u5224\u65ad\u65b0\u503c\u548c\u65e7\u503c\u662f\u5426\u76f8\u7b49<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0if\u00a0(oldValue\u00a0!=\u00a0element)\u00a0{<br><br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0\u590d\u5236\u65b0\u6570\u7ec4\uff0c\u65b0\u503c\u5728\u65b0\u6570\u7ec4\u4e2d\u5b8c\u6210<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0int\u00a0len\u00a0=\u00a0elements.length;<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Object[]\u00a0newElements\u00a0=\u00a0Arrays.copyOf(elements,\u00a0len);<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0newElements[index]\u00a0=\u00a0element;<br><br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0\u5c06array\u5f15\u7528\u6307\u5411\u65b0\u6570\u7ec4<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0setArray(newElements);<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}\u00a0else\u00a0{<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0Not\u00a0quite\u00a0a\u00a0no-op;\u00a0enssures\u00a0volatile\u00a0write\u00a0semantics<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0setArray(elements);<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return\u00a0oldValue;<br>\u00a0\u00a0\u00a0\u00a0}\u00a0finally\u00a0{<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0lock.unlock();<br>\u00a0\u00a0\u00a0\u00a0}<br>}<\/pre>\n\n\n\n<p>4.get\u65b9\u6cd5<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">public\u00a0E\u00a0get(int\u00a0index)\u00a0{<br> \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return get(getArray(), index);<br>}<br><br>final Object[] getArray() {<br> \u00a0\u00a0\u00a0return array;<br>}<\/pre>\n\n\n\n<ul><li><strong>\u5728\u4fee\u6539\u65f6\uff0c\u590d\u5236\u51fa\u4e00\u4e2a\u65b0\u6570\u7ec4\uff0c\u4fee\u6539\u7684\u64cd\u4f5c\u5728\u65b0\u6570\u7ec4\u4e2d\u5b8c\u6210\uff0c\u6700\u540e\u5c06\u65b0\u6570\u7ec4\u4ea4\u7531array\u53d8\u91cf\u6307\u5411<\/strong>\u3002<\/li><li><strong>\u5199\u52a0\u9501\uff0c\u8bfb\u4e0d\u52a0\u9501<\/strong><\/li><\/ul>\n\n\n\n<p>\u5e38\u7528\u7684\u65b9\u6cd5\u5b9e\u73b0\u6211\u4eec\u5df2\u7ecf\u57fa\u672c\u4e86\u89e3\u4e86\uff0c\u4f46\u8fd8\u662f\u4e0d\u77e5\u9053\u4e3a\u5565\u80fd\u591f\u5728\u5bb9\u5668\u904d\u5386\u7684\u65f6\u5019\u5bf9\u5176\u8fdb\u884c\u4fee\u6539\u800c\u4e0d\u629b\u51fa\u5f02\u5e38\u3002\u6240\u4ee5\uff0c\u6765\u770b\u4e00\u4e0b\u4ed6\u7684\u8fed\u4ee3\u5668\u5427\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">\u00a0\/\/\u00a01.\u00a0\u8fd4\u56de\u7684\u8fed\u4ee3\u5668\u662fCOWIterator<br>\u00a0\u00a0\u00a0\u00a0public\u00a0Iterator&lt;E>\u00a0iterator()\u00a0{<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return\u00a0new\u00a0COWIterator&lt;E>(getArray(),\u00a00);<br>\u00a0\u00a0\u00a0\u00a0}<br><br><br>\u00a0\u00a0\u00a0\u00a0\/\/\u00a02.\u00a0\u8fed\u4ee3\u5668\u7684\u6210\u5458\u5c5e\u6027<br>\u00a0\u00a0\u00a0\u00a0private\u00a0final\u00a0Object[]\u00a0snapshot;<br>\u00a0\u00a0\u00a0\u00a0private\u00a0int\u00a0cursor;<br><br>\u00a0\u00a0\u00a0\u00a0\/\/\u00a03.\u00a0\u8fed\u4ee3\u5668\u7684\u6784\u9020\u65b9\u6cd5<br>\u00a0\u00a0\u00a0\u00a0private\u00a0COWIterator(Object[]\u00a0elements,\u00a0int\u00a0initialCursor)\u00a0{<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0cursor\u00a0=\u00a0initialCursor;<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0snapshot\u00a0=\u00a0elements;<br>\u00a0\u00a0\u00a0\u00a0}<br><br>\u00a0\u00a0\u00a0\u00a0\/\/\u00a04.\u00a0\u8fed\u4ee3\u5668\u7684\u65b9\u6cd5...<br>\u00a0\u00a0\u00a0\u00a0public\u00a0E\u00a0next()\u00a0{<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0if\u00a0(!\u00a0hasNext())<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0throw\u00a0new\u00a0NoSuchElementException();<br>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0return\u00a0(E)\u00a0snapshot[cursor++];<br>\u00a0\u00a0\u00a0\u00a0}<br><br>\u00a0\u00a0\u00a0\u00a0\/\/....\u00a0\u53ef\u4ee5\u53d1\u73b0\u7684\u662f\uff0c\u8fed\u4ee3\u5668\u6240\u6709\u7684\u64cd\u4f5c\u90fd\u57fa\u4e8esnapshot\u6570\u7ec4\uff0c\u800csnapshot\u662f\u4f20\u9012\u8fdb\u6765\u7684array\u6570\u7ec4<\/pre>\n\n\n\n<p>\u8fed\u4ee3\u5668\u64cd\u4f5c\u7684\u662f\u539f\u59cb\u5bf9\u8c61\uff0c\u6240\u4ee5\u4e0d\u4f1a\u5e76\u53d1\u4fee\u6539\u3002<\/p>\n\n\n\n<p class=\"has-text-color has-bright-red-color\">\u770b\u4e86\u4e0a\u9762\u7684\u5b9e\u73b0\u6e90\u7801\uff0c\u6211\u4eec\u5e94\u8be5\u4e5f\u5927\u6982\u80fd\u5206\u6790\u51faCopyOnWriteArrayList\u7684\u7f3a\u70b9\u4e86\u3002<\/p>\n\n\n\n<ul><li><strong>\u5185\u5b58\u5360\u7528<\/strong>\uff1a\u5982\u679cCopyOnWriteArrayList\u7ecf\u5e38\u8981\u589e\u5220\u6539\u91cc\u9762\u7684\u6570\u636e\uff0c\u7ecf\u5e38\u8981\u6267\u884c<code>add()\u3001set()\u3001remove()<\/code>\u7684\u8bdd\uff0c\u90a3\u662f\u6bd4\u8f83\u8017\u8d39\u5185\u5b58\u7684\u3002<ul><li>\u56e0\u4e3a\u6211\u4eec\u77e5\u9053\u6bcf\u6b21`add()\u3001set()\u3001remove()`\u8fd9\u4e9b\u589e\u5220\u6539\u64cd\u4f5c\u90fd\u8981<strong>\u590d\u5236\u4e00\u4e2a\u6570\u7ec4<\/strong>\u51fa\u6765\u3002<\/li><\/ul><\/li><li><strong>\u6570\u636e\u4e00\u81f4\u6027<\/strong>\uff1aCopyOnWrite\u5bb9\u5668<strong>\u53ea\u80fd\u4fdd\u8bc1\u6570\u636e\u7684\u6700\u7ec8\u4e00\u81f4\u6027\uff0c\u4e0d\u80fd\u4fdd\u8bc1\u6570\u636e\u7684\u5b9e\u65f6\u4e00\u81f4\u6027<\/strong>\u3002<ul><li>\u4ece\u4e0a\u9762\u7684\u4f8b\u5b50\u4e5f\u53ef\u4ee5\u770b\u51fa\u6765\uff0c\u6bd4\u5982\u7ebf\u7a0bA\u5728\u8fed\u4ee3CopyOnWriteArrayList\u5bb9\u5668\u7684\u6570\u636e\u3002\u7ebf\u7a0bB\u5728\u7ebf\u7a0bA\u8fed\u4ee3\u7684\u95f4\u9699\u4e2d\u5c06CopyOnWriteArrayList\u90e8\u5206\u7684\u6570\u636e\u4fee\u6539\u4e86(\u5df2\u7ecf\u8c03\u7528`setArray()`\u4e86)\u3002\u4f46\u662f\u7ebf\u7a0bA\u8fed\u4ee3\u51fa\u6765\u7684\u662f\u539f\u6709\u7684\u6570\u636e\u3002<\/li><li><\/li><\/ul><\/li><\/ul>\n\n\n\n<p>CopyOnWriteArraySet\u7684\u539f\u7406\u5c31\u662fCopyOnWriteArrayList\u3002<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">private final CopyOnWriteArrayList<e>\u00a0al;\u00a0\u00a0\u00a0\u00a0<\/e><br><e>public\u00a0CopyOnWriteArraySet()\u00a0{\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/e><br><e>    al = new CopyOnWriteArrayList<e>();\u00a0\u00a0\u00a0\u00a0<\/e><\/e><br><e><e>}<\/e><\/e><\/pre>\n\n\n\n<p>\u53c2\u8003\uff1a<a href=\"https:\/\/mp.weixin.qq.com\/s?__biz=MzI4Njg5MDA5NA==&amp;mid=2247484380&amp;idx=1&amp;sn=c1aa61d29818005f886c61575d2a5d36&amp;chksm=ebd742dddca0cbcb4c8d5792cccfb774a268e64d2b65a94dd0781c17a73bfadf4f930c33f4be&amp;scene=21###wechat_redirect\">https:\/\/mp.weixin.qq.com\/s?__biz=MzI4Njg5MDA5NA==&amp;mid=2247484380&amp;idx=1&amp;sn=c1aa61d29818005f886c61575d2a5d36&amp;chksm=ebd742dddca0cbcb4c8d5792cccfb774a268e64d2b65a94dd0781c17a73bfadf4f930c33f4be&amp;scene=21###wechat_redirect<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>CopyOnWrite\u6280\u672f\uff0c\u4e3b\u8981\u5904\u7406\u591a\u7ebf\u7a0b\u5e76\u53d1\u8bbf\u95ee\u7684\u95ee\u9898\u3002\u666e\u901a\u7684ArrayList\uff0c\u5982\u679c\u5e76\u53d1\u4fee\u6539\uff0c\u4f1a\u62a5\u4e00\u4e2a\u5e76\u53d1 [&hellip;]<\/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":[56],"_links":{"self":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/1127"}],"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=1127"}],"version-history":[{"count":33,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/1127\/revisions"}],"predecessor-version":[{"id":1160,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/1127\/revisions\/1160"}],"wp:attachment":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1127"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1127"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1127"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}