{"id":2741,"date":"2018-05-01T09:14:57","date_gmt":"2018-05-01T01:14:57","guid":{"rendered":"http:\/\/www.xttblog.com\/?p=2741"},"modified":"2018-05-01T09:14:57","modified_gmt":"2018-05-01T01:14:57","slug":"java-hashmap-hashtable-hashset-concorrenthashmap","status":"publish","type":"post","link":"https:\/\/www.xttblog.com\/?p=2741","title":{"rendered":"java HashMap\/HashTable\/HashSet\/ConcorrentHashMap"},"content":{"rendered":"<p>\n\tJava \u4e2d\u4e3b\u8981\u4e0e hash \u6709\u5173\u4e14\u5e38\u7528\u76844\u4e2a\u7c7b\uff1aHashMap\u3001HashTable\u3001HashSet\u3001ConcorrentHashMap\u3002\u672c\u6587\u5c06\u4ecb\u7ecd\u5b83\u4eec\u7684\u4e00\u4e9b\u7528\u6cd5\u548c\u539f\u7406\u3002\n<\/p>\n<h2>\n\tHashMap<br \/>\n<\/h2>\n<p>\n\tHashMap\u662f\u57fa\u4e8ehashing\u7684\u539f\u7406\uff0c\u4f7f\u7528put(key, value)\u5b58\u50a8\u5bf9\u8c61\u5230HashMap\u4e2d\uff0c\u4f7f\u7528get(key)\u4eceHashMap\u4e2d\u83b7\u53d6\u5bf9\u8c61\u3002\u5f53\u7ed9put()\u65b9\u6cd5\u4f20\u9012\u952e\u548c\u503c\u65f6\uff0c\u5148\u5bf9\u952e\u8c03\u7528 hashCode()\u65b9\u6cd5\uff0c\u8fd4\u56de\u7684hashCode\u7528\u4e8e\u627e\u5230bucket\u4f4d\u7f6e\u6765\u50a8\u5b58Map.Entry\u5bf9\u8c61\u3002\u5f53\u4e24\u4e2a\u952e\u7684hashcode\u76f8\u540c\uff0c\u5b83\u4eec\u7684bucket\u4f4d\u7f6e\u76f8\u540c\uff0c&lsquo;\u78b0\u649e&rsquo;\u4f1a\u53d1\u751f\u3002\u56e0\u4e3aHashMap\u4f7f\u7528\u94fe\u8868\u5b58\u50a8\u5bf9\u8c61\uff0c\u8fd9\u4e2aEntry(\u5305\u542b\u6709\u952e\u503c\u5bf9\u7684Map.Entry\u5bf9\u8c61)\u4f1a\u5b58\u50a8\u5728\u94fe\u8868\u4e2d\u3002\u4ece\u800c\u89e3\u51b3\u78b0\u649e\u95ee\u9898\u3002\u6216\u8005\u503c\u65f6\uff0c\u627e\u5230bucket\u4f4d\u7f6e\u4e4b\u540e\uff0c\u4f1a\u8c03\u7528keys.equals()\u65b9\u6cd5\u904d\u5386\u7684\u627e\u5230\u94fe\u8868\u4e2d\u6b63\u786e\u7684\u8282\u70b9\uff0c\u6700\u7ec8\u627e\u5230\u8981\u627e\u7684\u503c\u5bf9\u8c61\u3002\u5c3d\u91cf\u4f7f\u7528\u4e0d\u53ef\u53d8\u7684\u3001\u58f0\u660e\u4f5cfinal\u7684\u5bf9\u8c61\uff0c\u5e76\u4e14\u91c7\u7528\u5408\u9002\u7684equals()\u548c hashCode()\u65b9\u6cd5\u7684\u8bdd\uff0c\u5c06\u4f1a\u51cf\u5c11\u78b0\u649e\u7684\u53d1\u751f\uff0c\u63d0\u9ad8\u6548\u7387\u3002\u5f53\u4e00\u4e2amap\u586b\u6ee1\u4e8675%\u7684bucket\u65f6\u5019\uff0c\u548c\u5176\u5b83\u96c6\u5408\u7c7b(\u5982ArrayList\u7b49)\u4e00\u6837\uff0c\u5c06\u4f1a\u521b\u5efa\u539f\u6765HashMap\u5927\u5c0f\u7684\u4e24\u500d\u7684bucket\u6570\u7ec4\uff0c\u6765\u91cd\u65b0\u8c03\u6574map\u7684\u5927\u5c0f\uff0c\u5e76\u5c06\u539f\u6765\u7684\u5bf9\u8c61\u653e \u5165\u65b0\u7684bucket\u6570\u7ec4\u4e2d\u3002\u8fd9\u4e2a\u8fc7\u7a0b\u53eb\u4f5crehashing\u3002\u5728\u8c03 \u6574\u5927\u5c0f\u7684\u8fc7\u7a0b\u4e2d\uff0c\u5b58\u50a8\u5728\u94fe\u8868\u4e2d\u7684\u5143\u7d20\u7684\u6b21\u5e8f\u4f1a\u53cd\u8fc7\u6765\uff0c\u907f\u514d\u5c3e\u90e8\u904d\u5386\u3002\n<\/p>\n<p>\n\t<img decoding=\"async\" alt=\"HashTable\" src=\"https:\/\/lark-assets-prod.oss-cn-hangzhou.aliyuncs.com\/2018\/png\/cb11b2b9-aa5c-46ca-b4a9-9539f2ba63ba.png\" style=\"width: 400px;height: 256px\" \/>\n<\/p>\n<h2>\n\tHashMap \u539f\u7406<br \/>\n<\/h2>\n<p>\n\tHashMap\u57fa\u4e8ehashing\u539f\u7406\uff0c\u6211\u4eec\u901a\u8fc7put()\u548cget()\u65b9\u6cd5\u50a8\u5b58\u548c\u83b7\u53d6\u5bf9\u8c61\u3002\u5f53\u6211\u4eec\u5c06\u952e\u503c\u5bf9\u4f20\u9012\u7ed9put()\u65b9\u6cd5\u65f6\uff0c\u5b83\u8c03\u7528\u952e\u5bf9\u8c61 \u7684hashCode()\u65b9\u6cd5\u6765\u8ba1\u7b97hashcode\uff0c\u8ba9\u540e\u627e\u5230bucket\u4f4d\u7f6e\u6765\u50a8\u5b58\u503c\u5bf9\u8c61\u3002\u5f53\u83b7\u53d6\u5bf9\u8c61\u65f6\uff0c\u901a\u8fc7\u952e\u5bf9\u8c61\u7684equals()\u65b9\u6cd5\u627e\u5230\u6b63\u786e\u7684 \u952e\u503c\u5bf9\uff0c\u7136\u540e\u8fd4\u56de\u503c\u5bf9\u8c61\u3002HashMap\u4f7f\u7528\u94fe\u8868\u6765\u89e3\u51b3\u78b0\u649e\u95ee\u9898\uff0c\u5f53\u53d1\u751f\u78b0\u649e\u4e86\uff0c\u5bf9\u8c61\u5c06\u4f1a\u50a8\u5b58\u5728\u94fe\u8868\u7684\u4e0b\u4e00\u4e2a\u8282\u70b9\u4e2d\u3002 HashMap\u5728\u6bcf\u4e2a\u94fe\u8868\u8282\u70b9\u4e2d\u50a8\u5b58\u952e\u503c\u5bf9\u5bf9\u8c61\u3002\n<\/p>\n<p>\n\t\u5f53\u4e24\u4e2a\u4e0d\u540c\u7684\u952e\u5bf9\u8c61\u7684hashcode\u76f8\u540c\u65f6\u4f1a\u53d1\u751f\u4ec0\u4e48\uff1f \u5b83\u4eec\u4f1a\u50a8\u5b58\u5728\u540c\u4e00\u4e2abucket\u4f4d\u7f6e\u7684\u94fe\u8868\u4e2d\u3002\u952e\u5bf9\u8c61\u7684equals()\u65b9\u6cd5\u7528\u6765\u627e\u5230\u952e\u503c\u5bf9\u3002\n<\/p>\n<h2>\n\tHashTable<br \/>\n<\/h2>\n<p>\n\tHashTable\u56e0\u4e3a\u5185\u90e8\u662f\u91c7\u7528synchronized\u6765\u4fdd\u8bc1\u7ebf\u7a0b\u5b89\u5168\u7684\uff0c\u4f46\u5728\u7ebf\u7a0b\u7ade\u4e89\u6fc0\u70c8\u7684\u60c5\u51b5\u4e0bHashTable\u7684\u6548\u7387\u4e0b\u964d\u5f97\u5f88\u5feb\u56e0\u4e3asynchronized\u5173\u952e\u5b57\u4f1a\u9020\u6210\u4ee3\u7801\u5757\u6216\u65b9\u6cd5\u6210\u4e3a\u4e3a\u4e34\u754c\u533a(\u5bf9\u540c\u4e00\u4e2a\u5bf9\u8c61\u52a0\u4e92\u65a5\u9501)\uff0c\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u8bbf\u95ee\u4e34\u754c\u533a\u7684\u4ee3\u7801\u65f6\uff0c\u5176\u4ed6\u7ebf\u7a0b\u4e5f\u8bbf\u95ee\u540c\u4e00\u4e34\u754c\u533a\u65f6\uff0c\u4f1a\u8fdb\u5165\u963b\u585e\u6216\u8f6e\u8be2\u72b6\u6001\u3002<br \/>\n\t\u7a76\u5176\u539f\u56e0\uff0c\u5b9e\u9645\u4e0a\u662f\u6709\u83b7\u53d6\u9501\u610f\u5411\u7684\u7ebf\u7a0b\u7684\u6570\u76ee\u589e\u52a0\uff0c\u4f46\u662f\u9501\u8fd8\u662f\u53ea\u6709\u5355\u4e2a\uff0c\u5bfc\u81f4\u5927\u91cf\u7684\u7ebf\u7a0b\u5904\u4e8e\u8f6e\u8be2\u6216\u963b\u585e\uff0c\u5bfc\u81f4\u540c\u4e00\u65f6\u95f4\u6bb5\u6709\u6548\u6267\u884c\u7684\u7ebf\u7a0b\u7684\u589e\u91cf\u8fdc\u4e0d\u53ca\u7ebf\u7a0b\u603b\u4f53\u589e\u91cf\u3002&nbsp;<br \/>\n\t\u5728\u67e5\u8be2\u65f6\uff0c\u5c24\u5176\u80fd\u591f\u4f53\u73b0\u51faCocurrentHashMap\u5728\u6548\u7387\u4e0a\u7684\u4f18\u52bf\uff0cHashTable\u4f7f\u7528Sychronized\u5173\u952e\u5b57\uff0c\u4f1a\u5bfc\u81f4\u540c\u65f6\u53ea\u80fd\u6709\u4e00\u4e2a\u67e5\u8be2\u5728\u6267\u884c\uff0c\u800cCocurrent\u5219\u4e0d\u91c7\u53d6\u52a0\u9501\u7684\u65b9\u6cd5\uff0c\u800c\u662f\u91c7\u7528volatile\u5173\u952e\u5b57\uff0c\u867d\u7136\u4e5f\u4f1a\u727a\u7272\u6548\u7387\uff0c\u4f46\u662f\u7531\u4e8eSychronized\u3002\n<\/p>\n<h2>\n\tHashMap\u4e0eHashTable\u6bd4\u8f83<br \/>\n<\/h2>\n<ol>\n<li>\n\t\t\u4e8c\u8005\u7684\u5b58\u50a8\u7ed3\u6784\u548c\u89e3\u51b3\u51b2\u7a81\u7684\u65b9\u6cd5\u90fd\u662f\u76f8\u540c\u7684\u3002\n\t<\/li>\n<li>\n\t\tHashTable\u5728\u4e0d\u6307\u5b9a\u5bb9\u91cf\u7684\u60c5\u51b5\u4e0b\u7684\u9ed8\u8ba4\u5bb9\u91cf\u4e3a11\uff0c\u800cHashMap\u4e3a16\uff0cHashtable\u4e0d\u8981\u6c42\u5e95\u5c42\u6570\u7ec4\u7684\u5bb9\u91cf\u4e00\u5b9a\u8981\u4e3a2\u7684\u6574\u6570\u6b21\u5e42\uff0c\u800cHashMap\u5219\u8981\u6c42\u4e00\u5b9a\u4e3a2\u7684\u6574\u6570\u6b21\u5e42\u3002\n\t<\/li>\n<li>\n\t\tHashtable\u4e2dkey\u548cvalue\u90fd\u4e0d\u5141\u8bb8\u4e3anull\uff0c\u800cHashMap\u4e2dkey\u548cvalue\u90fd\u5141\u8bb8\u4e3anull\uff08key\u53ea\u80fd\u6709\u4e00\u4e2a\u4e3anull\uff0c\u800cvalue\u5219\u53ef\u4ee5\u6709\u591a\u4e2a\u4e3anull\uff09\u3002\u4f46\u662f\u5982\u679c\u5728Hashtable\u4e2d\u6709\u7c7b\u4f3cput(null,null)\u7684\u64cd\u4f5c\uff0c\u7f16\u8bd1\u540c\u6837\u53ef\u4ee5\u901a\u8fc7\uff0c\u56e0\u4e3akey\u548cvalue\u90fd\u662fObject\u7c7b\u578b\uff0c\u4f46\u8fd0\u884c\u65f6\u4f1a\u629b\u51faNullPointerException\u5f02\u5e38\uff0c\u8fd9\u662fJDK\u7684\u89c4\u8303\u89c4\u5b9a\u7684\u3002\n\t<\/li>\n<li>\n\t\tHashtable\u6269\u5bb9\u65f6\uff0c\u5c06\u5bb9\u91cf\u53d8\u4e3a\u539f\u6765\u76842\u500d\u52a01\uff0c\u800cHashMap\u6269\u5bb9\u65f6\uff0c\u5c06\u5bb9\u91cf\u53d8\u4e3a\u539f\u6765\u76842\u500d\u3002\n\t<\/li>\n<li>\n\t\tHashtable\u8ba1\u7b97hash\u503c\uff0c\u76f4\u63a5\u7528key\u7684hashCode()\uff0c\u800cHashMap\u91cd\u65b0\u8ba1\u7b97\u4e86key\u7684hash\u503c\uff0cHashtable\u5728\u6c42hash\u503c\u5bf9\u5e94\u7684\u4f4d\u7f6e\u7d22\u5f15\u65f6\uff0c\u7528\u53d6\u6a21\u8fd0\u7b97\uff0c\u800cHashMap\u5728\u6c42\u4f4d\u7f6e\u7d22\u5f15\u65f6\uff0c\u5219\u7528\u4e0e\u8fd0\u7b97\uff0c\u4e14\u8fd9\u91cc\u4e00\u822c\u5148\u7528hash&amp;0x7FFFFFFF\u540e\uff0c\u518d\u5bf9length\u53d6\u6a21\uff0c&amp;0x7FFFFFFF\u7684\u76ee\u7684\u662f\u4e3a\u4e86\u5c06\u8d1f\u7684hash\u503c\u8f6c\u5316\u4e3a\u6b63\u503c\uff0c\u56e0\u4e3ahash\u503c\u6709\u53ef\u80fd\u4e3a\u8d1f\u6570\uff0c\u800c&amp;0x7FFFFFFF\u540e\uff0c\u53ea\u6709\u7b26\u53f7\u5916\u6539\u53d8\uff0c\u800c\u540e\u9762\u7684\u4f4d\u90fd\u4e0d\u53d8\u3002\n\t<\/li>\n<\/ol>\n<h2>\n\tHashSet<br \/>\n<\/h2>\n<p>\n\tHashSet\u662f\u57fa\u4e8eHashMap\u6765\u5b9e\u73b0\u7684\uff0c\u64cd\u4f5c\u5f88\u7b80\u5355\uff0c\u66f4\u50cf\u662f\u5bf9HashMap\u505a\u4e86\u4e00\u6b21&ldquo;\u5c01\u88c5&rdquo;\uff0c\u800c\u4e14\u53ea\u4f7f\u7528\u4e86HashMap\u7684key\u6765\u5b9e\u73b0\u5404\u79cd\u7279\u6027\u3002HashSet \u4e0d\u5141\u8bb8\u6709\u91cd\u590d\u5143\u7d20\u3002\n<\/p>\n<ul>\n<li>\n\t\thashset.add(E e)\uff1a\u8fd4\u56deboolean\u578b\uff0c\u5982\u679c\u6b64 set \u4e2d\u5c1a\u672a\u5305\u542b\u6307\u5b9a\u5143\u7d20\uff0c\u5219\u6dfb\u52a0\u6307\u5b9a\u5143\u7d20\uff1b\u5982\u679c\u6b64 set \u5df2\u5305\u542b\u8be5\u5143\u7d20\uff0c\u5219\u8be5\u8c03\u7528\u4e0d\u66f4\u6539 set \u5e76\u8fd4\u56de false\u3002\n\t<\/li>\n<li>\n\t\thashset.clear()\uff1a\u4ece\u6b64 set \u4e2d\u79fb\u9664\u6240\u6709\u5143\u7d20\u3002\n\t<\/li>\n<li>\n\t\thashset.remove(Object o)\uff1a\u5982\u679c\u6307\u5b9a\u5143\u7d20\u5b58\u5728\u4e8e\u6b64 set \u4e2d\uff0c\u5219\u5c06\u5176\u79fb\u9664\u3002\n\t<\/li>\n<li>\n\t\thashset.isEmpty()\uff1a\u5982\u679c\u6b64 set \u4e0d\u5305\u542b\u4efb\u4f55\u5143\u7d20\uff0c\u5219\u8fd4\u56de true\u3002\n\t<\/li>\n<li>\n\t\thashset.contains(Object o)\uff1a\u5982\u679c\u6b64 set \u5305\u542b\u6307\u5b9a\u5143\u7d20\uff0c\u5219\u8fd4\u56de true\u3002\n\t<\/li>\n<li>\n\t\thashset.size()\uff1a\u8fd4\u56de\u6b64 set \u4e2d\u7684\u5143\u7d20\u7684\u6570\u91cf\uff08set \u7684\u5bb9\u91cf\uff09\u3002\n\t<\/li>\n<\/ul>\n<h2>\n\tConcorrentHashMap<br \/>\n<\/h2>\n<p>\n\tConcurrentHashMap\u4e3a\u4e86\u63d0\u9ad8\u672c\u8eab\u7684\u5e76\u53d1\u80fd\u529b\uff0c\u5728\u5185\u90e8\u91c7\u7528\u4e86\u4e00\u4e2a\u53eb\u505aSegment\u7684\u7ed3\u6784\uff0c\u4e00\u4e2aSegment\u5176\u5b9e\u5c31\u662f\u4e00\u4e2a\u7c7bHashTable\u7684\u7ed3\u6784\uff0cSegment\u5185\u90e8\u7ef4\u62a4\u4e86\u4e00\u4e2a\u94fe\u8868\u6570\u7ec4\uff0cConcurrentHashMap\u5b9a\u4f4d\u4e00\u4e2a\u5143\u7d20\u7684\u8fc7\u7a0b\u9700\u8981\u8fdb\u884c\u4e24\u6b21Hash\u64cd\u4f5c\uff0c\u7b2c\u4e00\u6b21Hash\u5b9a\u4f4d\u5230Segment\uff0c\u7b2c\u4e8c\u6b21Hash\u5b9a\u4f4d\u5230\u5143\u7d20\u6240\u5728\u7684\u94fe\u8868\u7684\u5934\u90e8\uff0c\u56e0\u6b64\uff0c\u8fd9\u4e00\u79cd\u7ed3\u6784\u7684\u5e26\u6765\u7684\u526f\u4f5c\u7528\u662fHash\u7684\u8fc7\u7a0b\u8981\u6bd4\u666e\u901a\u7684HashMap\u8981\u957f\uff0c\u4f46\u662f\u5e26\u6765\u7684\u597d\u5904\u662f\u5199\u64cd\u4f5c\u7684\u65f6\u5019\u53ef\u4ee5\u53ea\u5bf9\u5143\u7d20\u6240\u5728\u7684Segment\u8fdb\u884c\u52a0\u9501\u5373\u53ef\uff0c\u4e0d\u4f1a\u5f71\u54cd\u5230\u5176\u4ed6\u7684Segment\uff0c\u8fd9\u6837\uff0c\u5728\u6700\u7406\u60f3\u7684\u60c5\u51b5\u4e0b\uff0cConcurrentHashMap\u53ef\u4ee5\u6700\u9ad8\u540c\u65f6\u652f\u6301Segment\u6570\u91cf\u5927\u5c0f\u7684\u5199\u64cd\u4f5c\uff08\u521a\u597d\u8fd9\u4e9b\u5199\u64cd\u4f5c\u90fd\u975e\u5e38\u5e73\u5747\u5730\u5206\u5e03\u5728\u6240\u6709\u7684Segment\u4e0a\uff09\uff0c\u6240\u4ee5\uff0cConcurrentHashMap\u7684\u5e76\u53d1\u80fd\u529b\u53ef\u4ee5\u5927\u5927\u7684\u63d0\u9ad8\u3002\n<\/p>\n<p>\n\t<img decoding=\"async\" alt=\"CurrentHashMap\" src=\"https:\/\/lark-assets-prod.oss-cn-hangzhou.aliyuncs.com\/2018\/png\/de290bbb-725c-44fc-8b5a-59b6c2a70558.png\" style=\"width: 554px;height: 295px\" \/>\n<\/p>\n<p>\n\t\u5229\u7528\u9501\u5206\u6bb5\u6280\u672f\u589e\u52a0\u4e86\u9501\u7684\u6570\u76ee\uff0c\u4ece\u800c\u4f7f\u4e89\u593a\u540c\u4e00\u628a\u9501\u7684\u7ebf\u7a0b\u7684\u6570\u76ee\u5f97\u5230\u63a7\u5236\u3002&nbsp;\n<\/p>\n<p>\n\tCurrentHashMap\u7684\u521d\u59cb\u5316\u4e00\u5171\u6709\u4e09\u4e2a\u53c2\u6570\uff0c\u4e00\u4e2ainitialCapacity\uff0c\u8868\u793a\u521d\u59cb\u7684\u5bb9\u91cf\uff0c\u4e00\u4e2aloadFactor\uff0c\u8868\u793a\u8d1f\u8f7d\u53c2\u6570\uff0c\u6700\u540e\u4e00\u4e2a\u662fconcurrentLevel\uff0c\u4ee3\u8868ConcurrentHashMap\u5185\u90e8\u7684Segment\u7684\u6570\u91cf\uff0cConcurrentLevel\u4e00\u7ecf\u6307\u5b9a\uff0c\u4e0d\u53ef\u6539\u53d8\uff0c\u540e\u7eed\u5982\u679cConcurrentHashMap\u7684\u5143\u7d20\u6570\u91cf\u589e\u52a0\u5bfc\u81f4ConrruentHashMap\u9700\u8981\u6269\u5bb9\uff0cConcurrentHashMap\u4e0d\u4f1a\u589e\u52a0Segment\u7684\u6570\u91cf\uff0c\u800c\u53ea\u4f1a\u589e\u52a0Segment\u4e2d\u94fe\u8868\u6570\u7ec4\u7684\u5bb9\u91cf\u5927\u5c0f\uff0c\u8fd9\u6837\u7684\u597d\u5904\u662f\u6269\u5bb9\u8fc7\u7a0b\u4e0d\u9700\u8981\u5bf9\u6574\u4e2aConcurrentHashMap\u505arehash\uff0c\u800c\u53ea\u9700\u8981\u5bf9Segment\u91cc\u9762\u7684\u5143\u7d20\u505a\u4e00\u6b21rehash\u5c31\u53ef\u4ee5\u4e86\u3002\n<\/p>\n<h2>\n\t\u9501\u5206\u6bb5\u6280\u672f<br \/>\n<\/h2>\n<p>\n\t\u5c31\u662f\u5bf9\u6570\u636e\u96c6\u8fdb\u884c\u5206\u6bb5\uff0c\u6bcf\u6bb5\u7ade\u4e89\u4e00\u628a\u9501\uff0c\u4e0d\u540c\u6570\u636e\u6bb5\u7684\u6570\u636e\u4e0d\u5b58\u5728\u9501\u7ade\u4e89\uff0c\u4ece\u800c\u6709\u6548\u63d0\u9ad8\u9ad8\u5e76\u53d1\u8bbf\u95ee\u6548\u7387\u3002\n<\/p>\n<p>\n\tCocurrentHashMap\u5728get\u65b9\u6cd5\u662f\u65e0\u9700\u52a0\u9501\u7684\uff0c\u56e0\u4e3a\u7528\u5230\u7684\u5171\u4eab\u53d8\u91cf\u90fd\u91c7\u7528volatile\u5173\u952e\u5b57\u4fee\u9970\uff0c\u4fdd\u8bc1\u5171\u4eab\u53d8\u91cf\u5728\u7ebf\u7a0b\u4e4b\u95f4\u7684\u53ef\u89c1\u6027(\u6bcf\u6b21\u8bfb\u53d6\u90fd\u5148\u540c\u6b65\u7f13\u5b58\u548c\u5185\u5b58\uff0c\u76f4\u63a5\u4ece\u5185\u5b58\u4e2d\u83b7\u53d6\u503c\uff0c\u867d\u7136\u4e0d\u662f\u539f\u5b50\u64cd\u4f5c\uff0c\u4f46\u6839\u636eJAVA\u5185\u5b58\u6a21\u578b\u7684happen before\u539f\u5219\uff0c\u5bf9volatile\u5b57\u6bb5\u7684\u5199\u5165\u64cd\u4f5c\u5148\u4e8e\u8bfb\u64cd\u4f5c\uff0c\u80fd\u591f\u4fdd\u8bc1\u4e0d\u4f1a\u810f\u8bfb),volatile\u4e3a\u4e86\u8ba9\u53d8\u91cf\u63d0\u4f9b\u7ebf\u7a0b\u4e4b\u95f4\u7684\u5185\u5b58\u53ef\u89c1\u6027\uff0c\u4f1a\u7981\u6b62\u7a0b\u5e8f\u6267\u884c\u7ed3\u679c\u7684\u91cd\u6392\u5e8f\uff08\u5bfc\u81f4\u7f13\u5b58\u4f18\u5316\u7684\u6548\u679c\u964d\u4f4e\uff09\u3002\n<\/p>\n<p>\n\tCocurrentHashMap\u662f\u7531Segment\u6570\u7ec4\u548cHashEntry\u6570\u7ec4\u7ec4\u6210\u3002\n<\/p>\n<p>\n\tSegment\u662f\u91cd\u5165\u9501(ReentrantLock),\u4f5c\u4e3a\u4e00\u4e2a\u6570\u636e\u6bb5\u7ade\u4e89\u9501\uff0c\u6bcf\u4e2aHashEntry\u4e00\u4e2a\u94fe\u8868\u7ed3\u6784\u7684\u5143\u7d20\uff0c\u5229\u7528Hash\u7b97\u6cd5\u5f97\u5230\u7d22\u5f15\u786e\u5b9a\u5f52\u5c5e\u7684\u6570\u636e\u6bb5\uff0c\u4e5f\u5c31\u662f\u5bf9\u5e94\u5230\u5728\u4fee\u6539\u65f6\u9700\u8981\u7ade\u4e89\u83b7\u53d6\u7684\u9501\u3002\n<\/p>\n<h2>\n\t\u64cd\u4f5c<br \/>\n<\/h2>\n<ol>\n<li>\n\t\tSegment\u7684get\u64cd\u4f5c\u662f\u4e0d\u9700\u8981\u52a0\u9501\u7684\u3002\u56e0\u4e3avolatile\u4fee\u9970\u7684\u53d8\u91cf\u4fdd\u8bc1\u4e86\u7ebf\u7a0b\u4e4b\u95f4\u7684\u53ef\u89c1\u6027\n\t<\/li>\n<li>\n\t\tSegment\u7684put\u64cd\u4f5c\u662f\u9700\u8981\u52a0\u9501\u7684\uff0c\u5728\u63d2\u5165\u65f6\u4f1a\u5148\u5224\u65adSegment\u91cc\u7684HashEntry\u6570\u7ec4\u662f\u5426\u4f1a\u8d85\u8fc7\u5bb9\u91cf(threshold),\u5982\u679c\u8d85\u8fc7\u9700\u8981\u5bf9\u6570\u7ec4\u6269\u5bb9\uff0c\u7ffb\u4e00\u500d\u3002\u7136\u540e\u5728\u65b0\u7684\u6570\u7ec4\u4e2d\u91cd\u65b0hash\uff0c\u4e3a\u4e86\u9ad8\u6548\uff0cCocurrentHashMap\u53ea\u4f1a\u5bf9\u9700\u8981\u6269\u5bb9\u7684\u5355\u4e2aSegment\u8fdb\u884c\u6269\u5bb9\n\t<\/li>\n<li>\n\t\tCocurrentHashMap\u83b7\u53d6size\u7684\u65f6\u5019\u8981\u7edf\u8ba1Segments\u4e2d\u7684HashEntry\u7684\u548c\uff0c\u5982\u679c\u4e0d\u5bf9\u4ed6\u4eec\u90fd\u52a0\u9501\u7684\u8bdd\uff0c\u65e0\u6cd5\u907f\u514d\u6570\u636e\u7684\u4fee\u6539\u9020\u6210\u7684\u9519\u8bef\uff0c\u4f46\u662f\u5982\u679c\u90fd\u52a0\u9501\u7684\u8bdd\uff0c\u6548\u7387\u53c8\u5f88\u4f4e\u3002\u6240\u4ee5CoccurentHashMap\u5728\u5b9e\u73b0\u7684\u65f6\u5019\uff0c\u5de7\u5999\u5730\u5229\u7528\u4e86\u5728\u7d2f\u52a0\u8fc7\u7a0b\u4e2d\u53d1\u751f\u53d8\u5316\u7684\u51e0\u7387\u5f88\u5c0f\u7684\u5ba2\u89c2\u6761\u4ef6\uff0c\u5728\u83b7\u53d6count\u65f6\uff0c\u4e0d\u52a0\u9501\u7684\u8ba1\u7b97\u4e24\u6b21\uff0c\u5982\u679c\u4e24\u6b21\u4e0d\u76f8\u540c\uff0c\u5728\u91c7\u7528\u52a0\u9501\u7684\u8ba1\u7b97\u65b9\u6cd5\u3002\u91c7\u7528\u4e86\u4e00\u4e2a\u9ad8\u6548\u7387\u7684\u526a\u679d\u9632\u6b62\u5f88\u5927\u6982\u7387\u5730\u51cf\u5c11\u4e86\u4e0d\u5fc5\u8981\u989d\u52a0\u9501\u3002\n\t<\/li>\n<\/ol>\n<!-- <audio autoplay=\"autoplay\" height=\"100\" width=\"100\" hidden=\"true\"><source src=\"https:\/\/c.coka.la\/orAvPR.mp3\" type=\"audio\/mp3\"\/><\/audio><img decoding=\"async\" src=\"https:\/\/images.weserv.nl\/?url=https:\/\/ws3.sinaimg.cn\/large\/8fa5dcfcgy1g4em3rzar5j20ib089ae0.jpg\" alt=\"\u4e1a\u4f59\u8349\u516c\u4f17\u53f7\"\/> --><p><!-- <img decoding=\"async\" src=\"https:\/\/raw.githubusercontent.com\/xmt1139057136\/xttblog\/master\/8fa5dcfcgy1g4em3rzar5j20ib089ae0.jpg\" alt=\"\u4e1a\u4f59\u8349\u516c\u4f17\u53f7\"\/>--><img decoding=\"async\" src=\"https:\/\/saas.51autoparts.cn\/api\/admin\/sys-file\/oss\/file?fileName=84db51f8561e448f9a4fda2eff0811f9.jpg\" alt=\"\u4e1a\u4f59\u8349\u516c\u4f17\u53f7\"\/><\/p><p>\u6700\u540e\uff0c\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u4e2a\u4eba\u5fae\u4fe1\u516c\u4f17\u53f7\uff1a\u4e1a\u4f59\u8349\uff08yyucao\uff09\uff01<b>\u53ef\u52a0\u4f5c\u8005\u5fae\u4fe1\u53f7\uff1a<font color=\"red\">xttblog2<\/font>\u3002\u5907\u6ce8\uff1a\u201c1\u201d\uff0c\u6dfb\u52a0\u535a\u4e3b\u5fae\u4fe1\u62c9\u4f60\u8fdb\u5fae\u4fe1\u7fa4\u3002\u5907\u6ce8\u9519\u8bef\u4e0d\u4f1a\u540c\u610f\u597d\u53cb\u7533\u8bf7\u3002<\/b>\u518d\u6b21\u611f\u8c22\u60a8\u7684\u5173\u6ce8\uff01\u540e\u7eed\u6709\u7cbe\u5f69\u5185\u5bb9\u4f1a\u7b2c\u4e00\u65f6\u95f4\u53d1\u7ed9\u60a8\uff01\u539f\u521b\u6587\u7ae0\u6295\u7a3f\u8bf7\u53d1\u9001\u81f3532009913@qq.com\u90ae\u7bb1\u3002\u5546\u52a1\u5408\u4f5c\u4e5f\u53ef\u6dfb\u52a0\u4f5c\u8005\u5fae\u4fe1\u8fdb\u884c\u8054\u7cfb\uff01<\/p><p>\u672c\u6587\u539f\u6587\u51fa\u5904\uff1a<a href=\"https:\/\/www.xttblog.com\">\u4e1a\u4f59\u8349<\/a>\uff1a &raquo; <a href=\"https:\/\/www.xttblog.com\/?p=2741\">java HashMap\/HashTable\/HashSet\/ConcorrentHashMap<\/a><\/p><!-- <div class=\"bd-reward-stl\"><button id=\"bdRewardBtn\"><span><\/span><\/button><\/div> -->","protected":false},"excerpt":{"rendered":"<p>Java \u4e2d\u4e3b\u8981\u4e0e hash \u6709\u5173\u4e14\u5e38\u7528\u76844\u4e2a\u7c7b\uff1aHashMap\u3001HashTable\u3001HashSet\u3001Conc [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[1164,462,1161,1162,660],"class_list":["post-2741","post","type-post","status-publish","format-standard","hentry","category-java","tag-concurrenthashmap","tag-hashcodebuilder","tag-hashmap","tag-hashtable","tag-hash"],"_links":{"self":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/2741","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2741"}],"version-history":[{"count":1,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/2741\/revisions"}],"predecessor-version":[{"id":2742,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/2741\/revisions\/2742"}],"wp:attachment":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2741"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2741"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2741"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}