{"id":175,"date":"2017-12-01T11:00:22","date_gmt":"2017-12-01T03:00:22","guid":{"rendered":"http:\/\/kaispace.cn\/?p=175"},"modified":"2017-12-01T11:00:22","modified_gmt":"2017-12-01T03:00:22","slug":"hashmap%e7%9a%84%e7%89%b9%e7%82%b9%e6%80%bb%e7%bb%93","status":"publish","type":"post","link":"https:\/\/blog.kaispace.cn\/?p=175","title":{"rendered":"HashMap\u7684\u7279\u70b9\u603b\u7ed3"},"content":{"rendered":"
HashMap<\/h5>\n

HashMap\u7684\u9ed8\u8ba4\u521d\u59cb\u957f\u5ea6\u4e3a16\uff0c\u4e14\u6bcf\u6b21\u6269\u5c55\u6216\u8005\u624b\u52a8\u521d\u59cb\u5316\u65f6\uff0c\u957f\u5ea6\u5fc5\u987b\u662f2\u7684\u5e42\uff0c\u4e4b\u6240\u4ee5\u9009\u62e916\uff0c\u662f\u4e3a\u4e86\u670d\u52a1\u4e8e\u4eceKey\u6620\u5c04\u5230Index\u7684Hash\u7b97\u6cd5\u3002<\/p>\n

\u4e3a\u5b9e\u73b0\u5c3d\u91cf\u5747\u5300\u7684Hash\u51fd\u6570\uff0cHashMap\u91c7\u7528\u4e86\u4f4d\u8fd0\u7b97\u7684\u65b9\u6cd5\u3002\u4ee5\u4e0b\u4e3a\u516c\u5f0f<\/p>\n

index = HashCode(key) & (Length -1)<\/p>\n

\u91c7\u752816\u7684\u521d\u59cb\u957f\u5ea6\u7684\u6700\u597d\u4f5c\u7528\u662f\u4f7f\u5f97\u5f97\u51fa\u7684Index\u7ed3\u679c\u5747\u5300\u5206\u5e03<\/p><\/blockquote>\n

\u7ebf\u7a0b\u5b89\u5168<\/h5>\n

\u9996\u5148HashMap\u662f\u7ebf\u7a0b\u4e0d\u5b89\u5168\u7684\u6570\u636e\u7ed3\u6784\uff0c\u5728\u9ad8\u5e76\u53d1\u60c5\u51b5\u4e0b\uff0c\u5bb9\u6613\u56e0\u4e3aRehash\u8fc7\u7a0b\u4e2d\u5f62\u6210\u73af\uff0c\u800c\u5bfc\u81f4\u540e\u671fGET\u65f6\u51fa\u73b0\u6b7b\u5faa\u73af\u3002\u7ebf\u7a0b\u5b89\u5168\u7684HashMap\u4e3aConcurrentHashMap<\/p>\n

Rehash\u662fHashMap\u7684Resize\uff08\u6269\u5c55\uff09\u4e2d\u7684\u4e00\u6b65\uff0c\u5f71\u54cdResize\u7684\u56e0\u7d20\u6709\u4e24\u4e2a,\u5206\u522b\u662f<\/p>\n

    \n
  1. Capacity\u5bb9\u91cf\uff08\u5f53\u524d\u957f\u5ea6\uff0c2\u7684\u5e42\uff09<\/li>\n
  2. LoadFactor\u8d1f\u8f7d\u56e0\u5b50\uff08\u9ed8\u8ba4\u4e3a0.75f\uff09<\/li>\n<\/ol>\n

    \u800c\u8861\u91cfHashMap\u662f\u5426\u9700\u8981Resize\u7684\u4f9d\u636e\u662f<\/p>\n

    HashMap.Size >= Capacity * LoadFactor<\/p><\/blockquote>\n

    HashMap\u7684\u6269\u5c55\u8fc7\u7a0b\u5982\u4e0b<\/p>\n

    1.\u6269\u5bb9<\/p>\n

    \u521b\u5efa\u4e00\u4e2a\u65b0\u7684Entry\u7a7a\u6570\u7ec4\uff0c\u957f\u5ea6\u4e3a\u539f\u6570\u7ec4\u7684\u4e24\u500d<\/p>\n

    2.Rehash<\/p>\n

    \u7531\u4e8eHash\u51fd\u6570 index=HashCode(Key)&(Length -1)<\/p>\n

    \u4e2d\u4f7f\u7528\u4e86Length\u8fd9\u4e00\u957f\u5ea6\u53d8\u91cf\uff0c\u56e0\u6b64\u6bcf\u6b21\u6269\u5c55\u90fd\u9700\u8981\u5168\u5c40Rehash<\/p>\n

    \u800c\u5728Rehash\u4e2d\u5f88\u5bb9\u6613\u7531\u4e8e\u5e76\u53d1\u95ee\u9898\u5bfc\u81f4\u51fa\u73b0\u94fe\u8868\u73af<\/p><\/blockquote>\n

    PUT\u65b9\u6cd5<\/h5>\n

    \u7531\u4e8eHashMap\u957f\u5ea6\u6709\u9650\uff0c\u5f53\u63d2\u5165\u7684Entry\u8d8a\u6765\u8d8a\u591a\u65f6\uff0c\u4e5f\u4f1a\u51fa\u73b0index\u51b2\u7a81\u7684\u60c5\u51b5\uff0c\u6b64\u65f6\u5e94\u6ce8\u610f\u5230HaspMap\u7684\u6bcf\u4e2a\u5143\u7d20\u4e0d\u4ec5\u4ec5\u53ea\u662f\u4e00\u4e2aEntry\u5bf9\u8c61\uff0c\u4e5f\u662f\u4e00\u4e2a\u94fe\u8868\u7684\u5934\u7ed3\u70b9\uff0c\u5f53\u65b0\u7684Entry\u6620\u5c04\u5230\u51b2\u7a81\u7684\u6570\u7ec4\u4f4d\u7f6e\u65f6\uff0c\u53ea\u9700\u8981\u63d2\u5165\u76f8\u5bf9\u5e94\u7684\u94fe\u8868\u5373\u53ef\u3002<\/p>\n

    \u63d2\u5165\u94fe\u8868\u7684\u65b9\u5f0f\u4f7f\u7528\u7684\u662f\u5934\u63d2\u6cd5<\/span><\/strong>\uff0c\u662f\u56e0\u4e3aHashMap\u53d1\u660e\u8005\u4efb\u52a1\uff0c\u540e\u63d2\u5165\u7684Entry\u88ab\u67e5\u627e\u7684\u53ef\u80fd\u6027\u66f4\u5927\u3002<\/span><\/span><\/span><\/p>\n

    GET\u65b9\u6cd5<\/h5>\n

    \u6839\u636e\u8f93\u5165\u7684Value\u503c\u7531Hash\u7b97\u6cd5\u8ba1\u7b97\u51faindex\uff0c\u7136\u540e\u4ece\u5bf9\u5e94index\u7684\u94fe\u8868\u4e2d\u904d\u5386\u67e5\u8be2\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"

    HashMap HashMap\u7684\u9ed8\u8ba4\u521d\u59cb\u957f\u5ea6\u4e3a16\uff0c\u4e14\u6bcf\u6b21\u6269\u5c55\u6216\u8005\u624b\u52a8\u521d\u59cb\u5316\u65f6\uff0c\u957f\u5ea6\u5fc5\u987b\u662f2\u7684\u5e42\uff0c\u4e4b\u6240\u4ee5\u9009\u62e91…<\/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":[],"_links":{"self":[{"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=\/wp\/v2\/posts\/175"}],"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=175"}],"version-history":[{"count":0,"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=\/wp\/v2\/posts\/175\/revisions"}],"wp:attachment":[{"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=175"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=175"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.kaispace.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=175"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}