{"id":215,"date":"2018-09-16T00:46:15","date_gmt":"2018-09-15T16:46:15","guid":{"rendered":"http:\/\/kaispace.cn\/?p=215"},"modified":"2018-09-16T00:46:15","modified_gmt":"2018-09-15T16:46:15","slug":"java%e5%ae%b9%e5%99%a8%e6%80%bb%e7%bb%93%ef%bc%88%e4%ba%8c%ef%bc%89","status":"publish","type":"post","link":"https:\/\/blog.kaispace.cn\/?p=215","title":{"rendered":"Java\u5bb9\u5668\u603b\u7ed3\uff08\u4e8c\uff09"},"content":{"rendered":"<h1>\u57fa\u4e8eMap<\/h1>\n<p>Map\u662f\u57fa\u4e8eK-V\u7ed3\u6784\u7684\u5bb9\u5668,key\u4e0d\u53ef\u91cd\u590d<\/p>\n<h2>1.1 HashMap\uff08<span style=\"color: #ff0000;\">\u7ebf\u7a0b\u4e0d\u5b89\u5168<\/span>|\u65e0\u5e8f\u65e0\u91cd\u590d<span style=\"color: #ff0000;\">\u652f\u6301Null\u503c<\/span>,\u7ee7\u627f\u4e8eAbstractMap\uff09<\/h2>\n<p>key\u7684\u7ef4\u62a4\u65b9\u5f0f\u4e0eHashSet\u76f8\u540c,\u901a\u8fc7equals+Hashcode\u5224\u65ad\u952e\u662f\u5426\u91cd\u590d\uff0c\u5229\u7528Hashcode\u51b3\u5b9a\u987a\u5e8f\u3002<\/p>\n<h2>1.1.1 LinkedHashMap\uff08\u6709\u5e8f\u4f46\u53ea\u662f\u63d2\u5165\u7684\u987a\u5e8f\uff09<\/h2>\n<p>LinkedHashMap\u4e5f\u4f7f\u7528\u53cc\u5411\u94fe\u8868\u6765\u7ef4\u62a4key-value\u5bf9\u7684\u6b21\u5e8f\uff0c\u8be5\u94fe\u8868\u8d1f\u8d23\u7ef4\u62a4Map\u7684\u8fed\u4ee3\u987a\u5e8f\uff0c\u4e0ekey-value\u5bf9\u7684\u63d2\u5165\u987a\u5e8f\u4e00\u81f4<\/p>\n<h2>1.2 Hashtable\uff08<span style=\"color: #ff0000;\">\u7ebf\u7a0b\u5b89\u5168<\/span>|\u65e0\u5e8f\u65e0\u91cd\u590d<span style=\"color: #ff0000;\">\u4e0d\u652f\u6301Null\u503c<\/span>,\u7ee7\u627f\u4e8eDictionary\uff08\u5df2\u5e9f\u5f03\uff09\uff09<\/h2>\n<p>\u76f8\u8f83\u4e8eHashMap\u9664\u4e86\u7ee7\u627f\u4e8e\u4e0d\u540c\u62bd\u8c61\u7c7b\u4ee5\u53ca\u5bf9Null\u503c\u7684\u652f\u6301\u4e0e\u5426\u533a\u522b\u5916\uff0c\u8fd8\u5728\u4e8e\u5bf9\u4e8e\u5927\u5c0f\u7684\u9009\u62e9\u4e0a\uff0cHashTable\u5728\u589e\u5bb9\u65f6\u4f1a\u9009\u7528<span style=\"color: #ff0000;\">\u7d20\u6570<\/span>\uff0c\u8fd9\u5bf9Hash\u540e\u987a\u5e8f\u5206\u5e03\u5747\u5300\u6709\u8f83\u5927\u4f5c\u7528,\u800cHashMap\u5219\u662f\u9009\u62e9<span style=\"color: #ff0000;\">2\u7684\u5e42\u6b21\u65b9<\/span>\u4f5c\u4e3a\u5bb9\u91cf\uff0c\u867d\u7136\u4f1a\u5bfc\u81f4\u5206\u5e03\u4e0d\u5747\uff0c\u4f46\u662f\u5728Hash\u901f\u5ea6\u4e0a\u660e\u663e\u4f18\u4e8eHashtable\uff08\u5728Hash\u7684\u65f6\u5019\u4e0d\u9700\u8981\u505a\u9664\u6cd5\u53ea\u9700\u8981\u4f4d\u7684\u4e0e\u8fd0\u7b97,\u800c\u4f4d\u8fd0\u7b97\u901f\u5ea6\u662f\u5feb\u4e8e\u666e\u901a\u7684\u8fd0\u7b97\u7684\uff09<\/p>\n<h2>1.2.1 Properties<\/h2>\n<p>\u5bf9\u4e8e\u6211\u6765\u8bb2Properties\u662f\u4e00\u4e2a\u5de5\u5177\u7c7b\uff08\u81ea\u8ba4\u4e3a\uff09,\u4f46\u662f\u7531\u4e8e\u5b83\u662f\u7ee7\u627f\u4e8eHashTable\uff0c\u5229\u7528HashTable\u6765\u7ef4\u62a4\u5c5e\u6027\u8868\uff0c\u56e0\u6b64\u4e5f\u5f52\u5e76\u5230\u5bb9\u5668\u7c7b\u91cc\u9762\u6765\u3002<br \/>\n\u901a\u8fc7\u8bfb\u53d6\uff08\u5185\u5b58\u6216\u6587\u4ef6\u4e2d\uff09\u5c5e\u6027\u6765\u7ef4\u62a4\u4e00\u4e2aHashTable\u3002<\/p>\n<h2>1.3 SortMap(<span style=\"color: #ff0000;\">\u63a5\u53e3<\/span>)<\/h2>\n<h2>1.3.1 TreeMap\uff08\u975e\u540c\u6b65\u7ebf\u7a0b\u4e0d\u5b89\u5168\u6709\u5e8f|\u57fa\u4e8e\u7ea2\u9ed1\u6811\u8fdb\u884c\u7ef4\u62a4\u7684Map\uff09<\/h2>\n<p>\u7ea2\u9ed1\u6811\u8be6\u89e3<a href=\"http:\/\/www.cnblogs.com\/skywang12345\/p\/3245399.html\">\u7ea2\u9ed1\u6811<\/a><br \/>\n\u7b80\u5355\u6765\u8bf4\u7ea2\u9ed1\u6811\u662f\u4e00\u9897\u4e8c\u53c9\u67e5\u627e\u6811\uff0c\u901a\u8fc7\u7ef4\u62a4\u5176\u987a\u5e8f(\u904d\u5386\u987a\u5e8fLRM)\u4ece\u800c\u8fbe\u5230\u904d\u5386\u65f6\u95f4\u590d\u6742\u5ea6o(logn)\u3002<\/p>\n<h2>1.4 WeakHashMap<\/h2>\n<p>WeakHashMap\u4e0eHashMap\u7684\u7528\u6cd5\u57fa\u672c\u76f8\u4f3c\u3002\u533a\u522b\u5728\u4e8e\uff0cHashMap\u7684key\u4fdd\u7559\u4e86\u5bf9\u5b9e\u9645\u5bf9\u8c61\u7684&#8221;<span style=\"color: #ff0000;\">\u5f3a\u5f15\u7528<\/span>&#8220;\uff0c\u8fd9\u610f\u5473\u7740\u53ea\u8981\u8be5HashMap\u5bf9\u8c61\u4e0d\u88ab\u9500\u6bc1\uff0c\u8be5HashMap\u6240\u5f15\u7528\u7684\u5bf9\u8c61\u5c31\u4e0d\u4f1a\u88ab\u5783\u573e\u56de\u6536\u3002<br \/>\n\u4f46WeakHashMap\u7684key\u53ea\u4fdd\u7559\u4e86\u5bf9\u5b9e\u9645\u5bf9\u8c61\u7684<span style=\"color: #ff0000;\">\u5f31\u5f15\u7528<\/span>\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679cWeakHashMap\u5bf9\u8c61\u7684key\u6240\u5f15\u7528\u7684\u5bf9\u8c61\u6ca1\u6709\u88ab\u5176\u4ed6\u5f3a\u5f15\u7528\u53d8\u91cf\u6240\u5f15\u7528\uff0c\u5219\u8fd9\u4e9bkey\u6240\u5f15\u7528\u7684\u5bf9\u8c61\u53ef\u80fd\u88ab\u5783\u573e\u56de\u6536\uff0c\u5f53\u5783\u573e\u56de\u6536\u4e86\u8be5key\u6240\u5bf9\u5e94\u7684\u5b9e\u9645\u5bf9\u8c61\u4e4b\u540e\uff0cWeakHashMap\u4e5f\u53ef\u80fd\u81ea\u52a8\u5220\u9664\u8fd9\u4e9bkey\u6240\u5bf9\u5e94\u7684key-value\u5bf9<\/p>\n<h2>1.5 IdentityHashMap<\/h2>\n<p>IdentityHashMap\u7684\u5b9e\u73b0\u673a\u5236\u4e0eHashMap\u57fa\u672c\u76f8\u4f3c\uff0c\u5728IdentityHashMap\u4e2d\uff0c\u5f53\u4e14\u4ec5\u5f53\u4e24\u4e2akey<span style=\"color: #ff0000;\">\u4e25\u683c\u76f8\u7b49<\/span>(key1 == key2)\u65f6\uff0cIdentityHashMap\u624d\u8ba4\u4e3a\u4e24\u4e2akey\u76f8\u7b49<\/p>\n<h2>1.6 EnumMap\uff08key\u90e8\u5206\u7c7b\u4f3c\u4e8eEnumMap\uff09<\/h2>\n<p>EnumMap\u662f\u4e00\u4e2a\u4e0e\u679a\u4e3e\u7c7b\u4e00\u8d77\u4f7f\u7528\u7684Map\u5b9e\u73b0\uff0cEnumMap\u4e2d\u6240\u6709key\u90fd\u5fc5\u987b\u662f\u5355\u4e2a\u679a\u4e3e\u7c7b\u7684\u679a\u4e3e\u503c\u3002\u521b\u5efaEnumMap\u65f6\u5fc5\u987b\u663e\u5f0f\u6216\u9690\u5f0f\u6307\u5b9a\u5b83\u5bf9\u5e94\u7684\u679a\u4e3e\u7c7b\u3002<br \/>\nEnumMap\u5728\u5185\u90e8\u4ee5\u6570\u7ec4\u5f62\u5f0f\u4fdd\u5b58\uff0c\u6240\u4ee5\u8fd9\u79cd\u5b9e\u73b0\u5f62\u5f0f\u975e\u5e38\u7d27\u51d1\u3001\u9ad8\u6548\u3002<br \/>\nEnumMap\u6839\u636ekey\u7684\u81ea\u7136\u987a\u5e8f\uff08\u5373\u679a\u4e3e\u503c\u5728\u679a\u4e3e\u7c7b\u4e2d\u7684\u5b9a\u4e49\u987a\u5e8f\uff09\u6765\u7ef4\u62a4\u6765\u7ef4\u62a4key-value\u5bf9\u7684\u6b21\u5e8f\u3002\u5f53\u7a0b\u5e8f\u901a\u8fc7keySet()\u3001entrySet()\u3001values()\u7b49\u65b9\u6cd5\u6765\u904d\u5386EnumMap\u65f6\u5373\u53ef\u770b\u5230\u8fd9\u79cd\u987a\u5e8f\u3002<br \/>\nEnumMap\u4e0d\u5141\u8bb8\u4f7f\u7528null\u4f5c\u4e3akey\u503c\uff0c\u4f46\u5141\u8bb8\u4f7f\u7528null\u4f5c\u4e3avalue\u3002\u5982\u679c\u8bd5\u56fe\u4f7f\u7528null\u4f5c\u4e3akey\u5c06\u629b\u51faNullPointerException\u5f02\u5e38\u3002\u5982\u679c\u4ec5\u4ec5\u53ea\u662f\u67e5\u8be2\u662f\u5426\u5305\u542b\u503c\u4e3anull\u7684key\u3001\u6216\u8005\u4ec5\u4ec5\u53ea\u662f\u4f7f\u7528\u5220\u9664\u503c\u4e3anull\u7684key\uff0c\u90fd\u4e0d\u4f1a\u629b\u51fa\u5f02\u5e38\u3002<br \/>\n<img loading=\"lazy\" class=\"alignnone size-full\" src=\"https:\/\/images0.cnblogs.com\/i\/532548\/201404\/262238192165666.jpg\" width=\"564\" height=\"391\" \/><\/p>\n<p>\u672c\u6587\u90e8\u5206\u501f\u9274\u4e8e:<a href=\"https:\/\/www.cnblogs.com\/LittleHann\/p\/3690187.html\">Java\u96c6\u5408\u7c7b<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u57fa\u4e8eMap Map\u662f\u57fa\u4e8eK-V\u7ed3\u6784\u7684\u5bb9\u5668,key\u4e0d\u53ef\u91cd\u590d 1.1 HashMap\uff08\u7ebf\u7a0b\u4e0d\u5b89\u5168|\u65e0\u5e8f\u65e0\u91cd\u590d\u652f\u6301N&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[2,9],"tags":[25,34],"_links":{"self":[{"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=\/wp\/v2\/posts\/215"}],"collection":[{"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=215"}],"version-history":[{"count":0,"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=\/wp\/v2\/posts\/215\/revisions"}],"wp:attachment":[{"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=215"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=215"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=215"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}