{"id":50,"date":"2022-03-30T16:04:31","date_gmt":"2022-03-30T08:04:31","guid":{"rendered":"https:\/\/blog.zjia.me\/?p=50"},"modified":"2026-06-19T21:02:47","modified_gmt":"2026-06-19T13:02:47","slug":"hashmap%e5%ba%95%e5%b1%82%e5%ae%9e%e7%8e%b0%e5%8e%9f%e7%90%86%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/blog.ttwow.top\/?p=50","title":{"rendered":"HashMap\u5e95\u5c42\u5b9e\u73b0\u539f\u7406\u8be6\u89e3"},"content":{"rendered":"<p>\u8f6c\u8f7d\uff1a<a href=\"https:\/\/zhuanlan.zhihu.com\/p\/351298116\"><a href=\"https:\/\/zhuanlan.zhihu.com\/p\/351298116\">https:\/\/zhuanlan.zhihu.com\/p\/351298116<\/a><\/a><\/p>\n<\/p>\n<h2>\u4e00\u3001\u5feb\u901f\u5165\u95e8<\/h2>\n<p>\u793a\u4f8b\uff1a\u6709\u4e00\u5b9a\u57fa\u7840\u7684\u5c0f\u4f19\u4f34\u4eec\u53ef\u4ee5\u9009\u62e9\u6027\u7684\u8df3\u8fc7\u8be5\u6b65\u9aa4<\/p>\n<p>HashMap\u662fJava\u7a0b\u5e8f\u5458\u4f7f\u7528\u9891\u7387\u6700\u9ad8\u7684\u7528\u4e8e\u6620\u5c04\u952e\u503c\u5bf9(key\u548cvalue)\u5904\u7406\u7684\u6570\u636e\u7c7b\u578b\u3002\u968f\u7740JDK\u7248\u672c\u7684\u8ddf\u65b0\uff0cJDK1.8\u5bf9HashMap\u5e95\u5c42\u7684\u5b9e\u73b0\u8fdb\u884c\u4e86\u4f18\u5316\uff0c\u5217\u5165\u5f15\u5165\u7ea2\u9ed1\u6811\u7684\u6570\u636e\u7ed3\u6784\u548c\u6269\u5bb9\u7684\u4f18\u5316\u7b49\u3002\u672c\u6587\u7ed3\u5408JDK1.7\u548cJDK1.8\u7684\u533a\u522b\uff0c\u6df1\u5165\u63a2\u8ba8HashMap\u7684\u6570\u636e\u7ed3\u6784\u5b9e\u73b0\u548c\u529f\u80fd\u539f\u7406\u3002<br \/>\nJava\u4e3a\u6570\u636e\u7ed3\u6784\u4e2d\u7684\u6620\u5c04\u5b9a\u4e49\u4e86\u4e00\u4e2a\u63a5\u53e3java.uti.Map\uff0c\u6b64\u63a5\u53e3\u4e3b\u8981\u6709\u56db\u4e2a\u5e38\u7528\u7684\u5b9e\u73b0\u7c7b\uff0c\u5206\u522b\u662fHashMap\uff0cLinkedHashMap\uff0cHashtable\uff0cTreeMap\uff0cIdentityHashMap\u3002\u672c\u7bc7\u6587\u7ae0\u4e3b\u8981\u8bb2\u89e3HashMap\u4ee5\u53ca\u5e95\u5c42\u5b9e\u73b0\u539f\u7406\u3002<\/p>\n<h3>1.HashMap\u7684\u5e38\u7528\u65b9\u6cd5<\/h3>\n<pre><code class=\"language-java\">\/\/        Hashmap\u5b58\u503c\uff1a----------------------------------\u300b .put(&quot;key&quot;,&quot;value&quot;)\uff1b ----------\u300b\u65e0\u8fd4\u56de\u503c\u3002\n\/\/\n\/\/        Hashmap\u53d6\u503c\uff1a----------------------------------\u300b .get(&quot;key&quot;)\uff1b-------------------\u300b \u8fd4\u56deValue\u7684\u7c7b\u578b\u3002\n\/\/\n\/\/        Hashmap\u5224\u65admap\u662f\u5426\u4e3a\u7a7a\uff1a-----------------------\u300b .isEmpty()\uff1b -------------------\u300b\u8fd4\u56deboolean\u7c7b\u578b\u3002\n\/\/\n\/\/        Hashmap\u5224\u65admap\u4e2d\u662f\u5426\u5b58\u5728\u8fd9\u4e2akey\uff1a--------------\u300b.containsKey(&quot;key&quot;)\uff1b------------\u300b\u8fd4\u56deboolean\u7c7b\u578b\u3002\n\/\/\n\/\/        Hashmap\u5224\u65admap\u4e2d\u662f\u5426\u542b\u6709value\uff1a----------------\u300b.containsValue(&quot;value&quot;)\uff1b-------\u300b\u8fd4\u56deboolean\u7c7b\u578b\u3002\n\/\/\n\/\/        Hashmap\u5220\u9664\u8fd9\u4e2akey\u503c\u4e0b\u7684value\uff1a----------------\u300b.remove(&quot;key&quot;)\uff1b-----------------\u300b\u8fd4\u56deValue\u7684\u7c7b\u578b\u3002\n\/\/\n\/\/        Hashmap\u663e\u793a\u6240\u6709\u7684value\u503c\uff1a---------------------\u300b.values()\uff1b --------------------\u300b\u8fd4\u56deValue\u7684\u7c7b\u578b\u3002\n\/\/\n\/\/        Hashmap\u663e\u793amap\u91cc\u7684\u503c\u5f97\u6570\u91cf\uff1a-------------------\u300b.size()\uff1b ----------------------\u300b\u8fd4\u56deint\u7c7b\u578b\n\/\/\n\/\/        HashMap\u663e\u793a\u5f53\u524d\u5df2\u5b58\u7684key\uff1a---------------------\u300b .keySet()\uff1b-------------------\u300b\u8fd4\u56deKey\u7684\u7c7b\u578b\u6570\u7ec4\u3002\n\/\/\n\/\/        Hashmap\u663e\u793a\u6240\u6709\u7684key\u548cvalue\uff1a-----------------\u300b.entrySet())\uff1b------------------\u300b\u8fd4\u56deKey=Value\u7c7b\u578b\u6570\u7ec4\u3002\n\/\/\n\/\/        Hashmap\u6dfb\u52a0\u53e6\u4e00\u4e2a\u540c\u4e00\u7c7b\u578b\u7684map\uff1a--------------\u300b.putAll(map)\uff1b -----------------\u300b(\u53c2\u6570\u4e3a\u53e6\u4e00\u4e2a\u540c\u4e00\u7c7b\u578b\u7684map)\u65e0\u8fd4\u56de\u503c\u3002\n\/\/\n\/\/        Hashmap\u5220\u9664\u8fd9\u4e2akey\u548cvalue\uff1a------------------\u300b.remove(&quot;key&quot;, &quot;value&quot;)\uff1b-------\u300b(\u5982\u679c\u8be5key\u503c\u4e0b\u9762\u5bf9\u5e94\u7684\u662f\u8be5value\u503c\u5219\u5220\u9664)\u8fd4\u56deboolean\u7c7b\u578b\u3002\n\/\/\n\/\/        Hashmap\u66ff\u6362\u8fd9\u4e2akey\u5bf9\u5e94\u7684value\u503c(JDK8\u65b0\u589e)\uff1a---\u300b.replace(&quot;key&quot;,&quot;value&quot;)\uff1b-------\u300b\u8fd4\u56de\u88ab\u66ff\u6362\u6389\u7684Value\u503c\u7684\u7c7b\u578b\u3002\n\/\/\n\/\/        \u514b\u9686Hashmap\uff1a-------------------------------\u300b.clone()\uff1b ---------------------\u300b\u8fd4\u56deobject\u7c7b\u578b\u3002\n\/\/\n\/\/        \u6e05\u7a7aHashmap\uff1a-------------------------------\u300b.clear()\uff1b ---------------------\u300b\u65e0\u8fd4\u56de\u503c\u3002<\/code><\/pre>\n<h3>2.HashMap\u7684\u51e0\u4e2a\u91cd\u8981\u77e5\u8bc6\u70b9<\/h3>\n<p>HashMap\u662f\u65e0\u5e8f\u4e14\u4e0d\u5b89\u5168\u7684\u6570\u636e\u7ed3\u6784\u3002<br \/>\nHashMap \u662f\u4ee5key\u2013value\u5bf9\u7684\u5f62\u5f0f\u5b58\u50a8\u7684\uff0ckey\u503c\u662f\u552f\u4e00\u7684\uff08\u53ef\u4ee5\u4e3anull\uff09\uff0c\u4e00\u4e2akey\u53ea\u80fd\u5bf9\u5e94\u7740\u4e00\u4e2avalue\uff0c\u4f46\u662fvalue\u662f\u53ef\u4ee5\u91cd\u590d\u7684\u3002<br \/>\nHashMap \u5982\u679c\u518d\u6b21\u6dfb\u52a0\u76f8\u540c\u7684key\u503c\uff0c\u5b83\u4f1a\u8986\u76d6key\u503c\u6240\u5bf9\u5e94\u7684\u5185\u5bb9\uff0c\u8fd9\u4e5f\u662f\u4e0eHashSet\u4e0d\u540c\u7684\u4e00\u70b9\uff0cSet\u901a\u8fc7add\u6dfb\u52a0\u76f8\u540c\u7684\u5bf9\u8c61\uff0c\u4e0d\u4f1a\u518d\u6dfb\u52a0\u5230Set\u4e2d\u53bb\u3002<br \/>\nHashMap \u63d0\u4f9b\u4e86get\u65b9\u6cd5\uff0c\u901a\u8fc7key\u503c\u53d6\u5bf9\u5e94\u7684value\u503c\uff0c\u4f46\u662fHashSet\u53ea\u80fd\u901a\u8fc7\u8fed\u4ee3\u5668Iterator\u6765\u904d\u5386\u6570\u636e\uff0c\u627e\u5bf9\u8c61\u3002<\/p>\n<h2>\u4e8c\u3001JDK7\u4e0eJDK8\u7684HashMap\u533a\u522b<\/h2>\n<p>\u65e2\u7136\u8bb2HashMap\uff0c\u90a3\u5c31\u4e0d\u5f97\u4e0d\u8bf4\u4e00\u4e0bJDK7\u4e0eJDK8\uff08\u53cajdk8\u4ee5\u540e\uff09\u7684HashMap\u6709\u4ec0\u4e48\u533a\u522b\uff1a<\/p>\n<p>jdk8\u4e2d\u6dfb\u52a0\u4e86\u7ea2\u9ed1\u6811\uff0c\u5f53\u94fe\u8868\u957f\u5ea6\u5927\u4e8e\u7b49\u4e8e8\u7684\u65f6\u5019\u94fe\u8868\u4f1a\u53d8\u6210\u7ea2\u9ed1\u6811<br \/>\n\u94fe\u8868\u65b0\u8282\u70b9\u63d2\u5165\u94fe\u8868\u7684\u987a\u5e8f\u4e0d\u540c\uff08jdk7\u662f\u63d2\u5165\u5934\u7ed3\u70b9\uff0cjdk8\u56e0\u4e3a\u8981\u628a\u94fe\u8868\u53d8\u4e3a\u7ea2 \u9ed1\u6811\u6240\u4ee5\u91c7\u7528\u63d2\u5165\u5c3e\u8282\u70b9\uff09<br \/>\nhash\u7b97\u6cd5\u7b80\u5316 ( jdk8 )<br \/>\nresize\u7684\u903b\u8f91\u4fee\u6539\uff08jdk7\u4f1a\u51fa\u73b0\u6b7b\u5faa\u73af\uff0cjdk8\u4e0d\u4f1a\uff09<\/p>\n<h2>\u4e09\u3001HashMap\u7684\u5bb9\u91cf\u4e0e\u6269\u5bb9\u673a\u5236<\/h2>\n<h3>1.HashMap\u7684\u9ed8\u8ba4\u8d1f\u8f7d\u56e0\u5b50<\/h3>\n<pre><code class=\"language-java\"> \/**\n     * The load factor used when none specified in constructor.\n     *\/\n    static final float DEFAULT_LOAD_FACTOR = 0.75f;\n    \/**\n     *\u9ed8\u8ba4\u7684\u8d1f\u8f7d\u56e0\u5b50\u662f0.75f,\u4e5f\u5c31\u662f75% \u8d1f\u8f7d\u56e0\u5b50\u7684\u4f5c\u7528\u5c31\u662f\u8ba1\u7b97\u6269\u5bb9\u9608\u503c\u7528\uff0c\u6bd4\u5982\u8bf4\u4f7f\u7528\n     *\u65e0\u53c2\u6784\u9020\u65b9\u6cd5\u521b\u5efa\u7684HashMap \u5bf9\u8c61\uff0c\u4ed6\u521d\u59cb\u957f\u5ea6\u9ed8\u8ba4\u662f16  \u9608\u503c = \u5f53\u524d\u957f\u5ea6 * 0.75  \u5c31\n     *\u80fd\u7b97\u51fa\u9608\u503c\uff0c\u5f53\u5f53\u524d\u957f\u5ea6\u5927\u4e8e\u7b49\u4e8e\u9608\u503c\u7684\u65f6\u5019HashMap\u5c31\u4f1a\u8fdb\u884c\u81ea\u52a8\u6269\u5bb9\n     *\/<\/code><\/pre>\n<p>\u9762\u8bd5\u7684\u65f6\u5019\uff0c\u9762\u8bd5\u5b98\u7ecf\u5e38\u4f1a\u95ee\u9053\u4e00\u4e2a\u95ee\u9898\uff1a\u4e3a\u4ec0\u4e48HashMap\u7684\u9ed8\u8ba4\u8d1f\u8f7d\u56e0\u5b50\u662f0.75\uff0c\u800c\u4e0d\u662f0.5\u6216\u8005\u662f\u6574\u65701\u5462\uff1f<br \/>\n\u7b54\u6848\u6709\u4e24\u79cd\uff1a<\/p>\n<p>\u9608\u503c(threshold) = \u8d1f\u8f7d\u56e0\u5b50(loadFactor) x \u5bb9\u91cf(capacity) \u6839\u636eHashMap\u7684\u6269\u5bb9\u673a\u5236\uff0c\u4ed6\u4f1a\u4fdd\u8bc1\u5bb9\u91cf(capacity)\u7684\u503c\u6c38\u8fdc\u90fd\u662f2\u7684\u5e42 \u4e3a\u4e86\u4fdd\u8bc1\u8d1f\u8f7d\u56e0\u5b50x\u5bb9\u91cf\u7684\u7ed3\u679c\u662f\u4e00\u4e2a\u6574\u6570\uff0c\u8fd9\u4e2a\u503c\u662f0.75(4\/3)\u6bd4\u8f83\u5408\u7406\uff0c\u56e0\u4e3a\u8fd9\u4e2a\u6570\u548c\u4efb\u4f552\u7684\u6b21\u5e42\u4e58\u79ef\u7ed3\u679c\u90fd\u662f\u6574\u6570\u3002<br \/>\n\u7406\u8bba\u4e0a\u6765\u8bb2\uff0c\u8d1f\u8f7d\u56e0\u5b50\u8d8a\u5927\uff0c\u5bfc\u81f4\u54c8\u5e0c\u51b2\u7a81\u7684\u6982\u7387\u4e5f\u5c31\u8d8a\u5927\uff0c\u8d1f\u8f7d\u56e0\u5b50\u8d8a\u5c0f\uff0c\u8d39\u7684\u7a7a\u95f4\u4e5f\u5c31\u8d8a\u5927,\u8fd9\u662f\u4e00\u4e2a\u65e0\u6cd5\u907f\u514d\u7684\u5229\u5f0a\u5173\u7cfb\uff0c\u6240\u4ee5\u901a\u8fc7\u4e00\u4e2a\u7b80\u5355\u7684\u6570\u5b66\u63a8\u7406\uff0c\u53ef\u4ee5\u6d4b\u7b97\u51fa\u8fd9\u4e2a\u6570\u503c\u57280.75\u5de6\u53f3\u662f\u6bd4\u8f83\u5408\u7406\u7684<\/p>\n<h3>2.HashMap\u7684\u6269\u5bb9\u673a\u5236<\/h3>\n<p>\u5199\u6570\u636e\u4e4b\u540e\u4f1a\u53ef\u80fd\u89e6\u53d1\u6269\u5bb9\uff0cHashMap\u7ed3\u6784\u5185\uff0c\u6211\u8bb0\u5f97\u6709\u4e00\u4e2a\u8bb0\u5f55\u5f53\u524d\u6570\u636e\u91cf\u7684\u5b57\u6bb5\uff0c\u8fd9\u4e2a\u6570\u636e\u91cf\u5b57\u6bb5\u5230\u8fbe\u6269\u5bb9\u9608\u503c\u7684\u8bdd\uff0c\u5b83\u5c31\u4f1a\u89e6\u53d1\u6269\u5bb9\u7684\u64cd\u4f5c<\/p>\n<pre><code class=\"language-java\">\u9608\u503c(threshold) = \u8d1f\u8f7d\u56e0\u5b50(loadFactor) x \u5bb9\u91cf(capacity)\n\u5f53HashMap\u4e2dtable\u6570\u7ec4(\u4e5f\u79f0\u4e3a\u6876)\u957f\u5ea6 &gt;= \u9608\u503c(threshold) \u5c31\u4f1a\u81ea\u52a8\u8fdb\u884c\u6269\u5bb9\u3002\n\n\u6269\u5bb9\u7684\u89c4\u5219\u662f\u8fd9\u6837\u7684\uff0c\u56e0\u4e3atable\u6570\u7ec4\u957f\u5ea6\u5fc5\u987b\u662f2\u7684\u6b21\u65b9\u6570\uff0c\u6269\u5bb9\u5176\u5b9e\u6bcf\u6b21\u90fd\u662f\u6309\u7167\u4e0a\u4e00\u6b21tableSize\u4f4d\u8fd0\u7b97\u5f97\u5230\u7684\u5c31\u662f\u505a\u4e00\u6b21\u5de6\u79fb1\u4f4d\u8fd0\u7b97\uff0c\n\u5047\u8bbe\u5f53\u524dtableSize\u662f16\u7684\u8bdd 16\u8f6c\u4e3a\u4e8c\u8fdb\u5236\u518d\u5411\u5de6\u79fb\u4e00\u4f4d\u5c31\u5f97\u5230\u4e8632 \u5373 16 &lt;&lt; 1 == 32 \u5373\u6269\u5bb9\u540e\u7684\u5bb9\u91cf\uff0c\u4e5f\u5c31\u662f\u8bf4\u6269\u5bb9\u540e\u7684\u5bb9\u91cf\u662f\u5f53\u524d\n\u5bb9\u91cf\u7684\u4e24\u500d\uff0c\u4f46\u8bb0\u4f4fHashMap\u7684\u6269\u5bb9\u662f\u91c7\u7528\u5f53\u524d\u5bb9\u91cf\u5411\u5de6\u4f4d\u79fb\u4e00\u4f4d\uff08newtableSize = tableSize &lt;&lt; 1\uff09\uff0c\u5f97\u5230\u7684\u6269\u5bb9\u540e\u5bb9\u91cf\uff0c\u800c\u4e0d\u662f\u5f53\u524d\u5bb9\u91cfx2<\/code><\/pre>\n<p>\u95ee\u9898\u53c8\u6765\u4e86\uff0c\u4e3a\u4ec0\u4e48\u8ba1\u7b97\u6269\u5bb9\u540e\u5bb9\u91cf\u8981\u91c7\u7528\u4f4d\u79fb\u8fd0\u7b97\u5462\uff0c\u600e\u4e48\u4e0d\u76f4\u63a5\u4e58\u4ee52\u5462\uff1f<br \/>\n\u8fd9\u4e2a\u95ee\u9898\u5c31\u6bd4\u8f83\u7b80\u5355\u4e86\uff0c\u56e0\u4e3acpu\u6bd5\u7adf\u5b83\u4e0d\u652f\u6301\u4e58\u6cd5\u8fd0\u7b97\uff0c\u6240\u6709\u7684\u4e58\u6cd5\u8fd0\u7b97\u5b83\u6700\u7ec8\u90fd\u662f\u518d\u6307\u4ee4\u5c42\u9762\u8f6c\u5316\u4e3a\u4e86\u52a0\u6cd5\u5b9e\u73b0\u7684\uff0c\u8fd9\u6837\u6548\u7387\u5f88\u4f4e\uff0c\u5982\u679c\u7528\u4f4d\u8fd0\u7b97\u7684\u8bdd\u5bf9cpu\u6765\u8bf4\u5c31\u975e\u5e38\u7684\u7b80\u6d01\u9ad8\u6548\u3002<\/p>\n<h3>3.HashMap\u4e2d\u6563\u5217\u8868\u6570\u7ec4\u521d\u59cb\u957f\u5ea6<\/h3>\n<pre><code class=\"language-java\"> \/**\n     * The default initial capacity - MUST be a power of two.\n     *\/\n    static final int DEFAULT_INITIAL_CAPACITY = 1 &lt;&lt; 4; \/\/ aka 16\n\n    \/**\n     * HashMap\u4e2d\u6563\u5217\u8868\u6570\u7ec4\u521d\u59cb\u957f\u5ea6\u4e3a 16 (1 &lt;&lt; 4)\n     * \u521b\u5efaHashMap\u7684\u65f6\u5019\u53ef\u4ee5\u8bbe\u7f6e\u521d\u59cb\u5316\u5bb9\u91cf\u548c\u8bbe\u7f6e\u8d1f\u8f7d\u56e0\u5b50\uff0c\n     * \u4f46HashMap\u4f1a\u81ea\u52a8\u4f18\u5316\u8bbe\u7f6e\u7684\u521d\u59cb\u5316\u5bb9\u91cf\u53c2\u6570\uff0c\u786e\u4fdd\u521d\u59cb\u5316\n     * \u5bb9\u91cf\u59cb\u7ec8\u4e3a2\u7684\u5e42\n     *\/<\/code><\/pre>\n<p>\u8001\u95ee\u9898\u53c8\u6765\u4e86\uff0c\u4e3a\u5565HashMap\u4e2d\u521d\u59cb\u5316\u5927\u5c0f\u4e3a\u4ec0\u4e48\u662f16\u5462\uff1f<\/p>\n<p>\u9996\u5148\u6211\u4eec\u770bhashMap\u7684\u6e90\u7801\u53ef\u77e5\u5f53\u65b0put\u4e00\u4e2a\u6570\u636e\u65f6\u4f1a\u8fdb\u884c\u8ba1\u7b97\u4f4d\u4e8etable\u6570\u7ec4(\u4e5f\u79f0\u4e3a\u6876)\u4e2d\u7684\u4e0b\u6807\uff1a<\/p>\n<p>int index =key.hashCode()&amp;(length-1);<\/p>\n<p>hahmap\u6bcf\u6b21\u6269\u5bb9\u90fd\u662f\u4ee5 2\u7684\u6574\u6570\u6b21\u5e42\u8fdb\u884c\u6269\u5bb9<\/p>\n<p>\u56e0\u4e3a\u662f\u5c06\u4e8c\u8fdb\u5236\u8fdb\u884c\u6309\u4f4d\u4e8e\uff0c(16-1) \u662f 1111,\u672b\u4f4d\u662f1\uff0c\u8fd9\u6837\u4e5f\u80fd\u4fdd\u8bc1\u8ba1\u7b97\u540e\u7684index\u65e2\u53ef\u4ee5\u662f\u5947\u6570\u4e5f\u53ef\u4ee5\u662f\u5076\u6570\uff0c\u5e76\u4e14\u53ea\u8981\u4f20\u8fdb\u6765\u7684key\u8db3\u591f\u5206\u6563\uff0c\u5747\u5300\u90a3\u4e48\u6309\u4f4d\u4e8e\u7684\u65f6\u5019\u83b7\u5f97\u7684index\u5c31\u4f1a\u51cf\u5c11\u91cd\u590d\uff0c\u8fd9\u6837\u4e5f\u5c31\u51cf\u5c11\u4e86hash\u7684\u78b0\u649e\u4ee5\u53cahashMap\u7684\u67e5\u8be2\u6548\u7387\u3002<\/p>\n<p>\u90a3\u4e48\u5230\u4e86\u8fd9\u91cc\u4f60\u4e5f\u8bb8\u4f1a\u95ee\uff1f \u90a3\u4e48\u5c31\u713616\u53ef\u4ee5\uff0c\u662f\u4e0d\u662f\u53ea\u8981\u662f2\u7684\u6574\u6570\u6b21\u5e42\u5c31\u53ef\u4ee5\u5462\uff1f<\/p>\n<p>\u7b54\u6848\u662f\u80af\u5b9a\u7684\u3002\u90a3\u4e3a\u4ec0\u4e48\u4e0d\u662f8,4\u5462\uff1f \u56e0\u4e3a\u662f8\u6216\u80054\u7684\u8bdd\u5f88\u5bb9\u6613\u5bfc\u81f4map\u6269\u5bb9\u5f71\u54cd\u6027\u80fd\uff0c\u5982\u679c\u5206\u914d\u7684\u592a\u5927\u7684\u8bdd\u53c8\u4f1a\u6d6a\u8d39\u8d44\u6e90\uff0c\u6240\u4ee5\u5c31\u4f7f\u752816\u4f5c\u4e3a\u521d\u59cb\u5927\u5c0f\u3002<\/p>\n<h2>\u56db\u3001HashMap\u7684\u7ed3\u6784<\/h2>\n<p>JDK7\u4e0eJDK8\u53ca\u4ee5\u540e\u7684HashMap\u7ed3\u6784\u4e0e\u5b58\u50a8\u539f\u7406\u6709\u6240\u4e0d\u540c\uff1a<br \/>\nJdk1.7\uff1a\u6570\u7ec4 + \u94fe\u8868 ( \u5f53\u6570\u7ec4\u4e0b\u6807\u76f8\u540c\uff0c\u5219\u4f1a\u5728\u8be5\u4e0b\u6807\u4e0b\u4f7f\u7528\u94fe\u8868)<br \/>\nJdk1.8\uff1a\u6570\u7ec4 + \u94fe\u8868 + \u7ea2\u9ed1\u6811 (\u9884\u503c\u4e3a8 \u5982\u679c\u94fe\u8868\u957f\u5ea6&lt;=8\u5219\u4f1a\u628a\u94fe\u8868\u53d8\u6210\u7ea2\u9ed1\u6811 )<br \/>\nJdk1.7\u4e2d\u94fe\u8868\u65b0\u5143\u7d20\u6dfb\u52a0\u5230\u94fe\u8868\u7684\u5934\u7ed3\u70b9,\u5148\u52a0\u5230\u94fe\u8868\u7684\u5934\u8282\u70b9,\u518d\u79fb\u5230\u6570\u7ec4\u4e0b\u6807\u4f4d\u7f6e<br \/>\nJdk1.8\u4e2d\u94fe\u8868\u65b0\u5143\u7d20\u6dfb\u52a0\u5230\u94fe\u8868\u7684\u5c3e\u7ed3\u70b9<br \/>\n(\u6570\u7ec4\u901a\u8fc7\u4e0b\u6807\u7d22\u5f15\u67e5\u8be2\uff0c\u6240\u4ee5\u67e5\u8be2\u6548\u7387\u975e\u5e38\u9ad8\uff0c\u94fe\u8868\u53ea\u80fd\u6328\u4e2a\u904d\u5386\uff0c\u6548\u7387\u975e\u5e38\u4f4e\u3002jdk1.8\u53ca\u4ee5<br \/>\n\u4e0a\u7248\u672c\u5f15\u5165\u4e86\u7ea2\u9ed1\u6811\uff0c\u5f53\u94fe\u8868\u7684\u957f\u5ea6\u5927\u4e8e\u6216\u7b49\u4e8e8\u7684\u65f6\u5019\u5219\u4f1a\u628a\u94fe\u8868\u53d8\u6210\u7ea2\u9ed1\u6811\uff0c\u4ee5\u63d0\u9ad8\u67e5\u8be2\u6548\u7387)<\/p>\n<h2>\u4e94\u3001HashMap\u5b58\u50a8\u539f\u7406\u4e0e\u5b58\u50a8\u6d41\u7a0b<\/h2>\n<h3>1.HashMap\u5b58\u50a8\u539f\u7406<\/h3>\n<p>\u83b7\u53d6\u5230\u4f20\u8fc7\u6765\u7684key\uff0c\u8c03\u7528hash\u7b97\u6cd5\u83b7\u53d6\u5230hash\u503c<br \/>\n\u83b7\u53d6\u5230hash\u503c\u4e4b\u540e\u8c03\u7528indexFor\u65b9\u6cd5\uff0c\u901a\u8fc7\u83b7\u53d6\u5230\u7684hash\u503c\u4ee5\u53ca\u6570\u7ec4\u7684\u957f\u5ea6\u7b97<br \/>\n\u51fa\u6570\u7ec4\u7684\u4e0b\u6807 (\u628a\u54c8\u5e0c\u503c\u548c\u6570\u7ec4\u5bb9\u91cf\u8f6c\u6362\u4e3a\u4e8c\u8fdb\uff0c\u518d\u5728\u6570\u7ec4\u5bb9\u91cf\u8303\u56f4\u5185\u4e0e\u54c8\u5e0c\u503c<br \/>\n\u8fdb\u884c\u4e00\u6b21\u4e0e\u8fd0\u7b97\uff0c\u540c\u4e3a1\u52191\uff0c\u4e0d\u7136\u5219\u4e3a0\uff0c\u5f97\u51fa\u6570\u7ec4\u7684\u4e0b\u6807\u503c\uff0c\u8fd9\u6837\u53ef\u4ee5\u4fdd\u8bc1\u8ba1\u7b97\u51fa\u7684\u6570\u7ec4\u4e0b\u6807\u4e0d\u4f1a\u5927\u4e8e\u5f53\u524d\u6570\u7ec4\u5bb9\u91cf)<br \/>\n\u628a\u4f20\u8fc7\u6765\u7684key\u548cvalue\u5b58\u5230\u8be5\u6570\u7ec4\u4e0b\u6807\u5f53\u4e2d\u3002<br \/>\n\u5982\u8be5\u6570\u7ec4\u4e0b\u6807\u4e0b\u4ee5\u53ca\u6709\u503c\u4e86\uff0c\u5219\u4f7f\u7528\u94fe\u8868\uff0cjdk7\u662f\u628a\u65b0\u589e\u5143\u7d20\u6dfb\u52a0\u5230\u5934\u90e8\u8282\u70b9 jdk8\u5219\u6dfb\u52a0\u5230\u5c3e\u90e8\u8282\u70b9\u3002<\/p>\n<h3>2.HashMap\u5b58\u50a8\u6d41\u7a0b<\/h3>\n<p>\u524d\u9762\u5bfb\u5740\u7b97\u6cd5\u90fd\u662f\u4e00\u6837\u7684\uff0c\u6839\u636ekey\u7684hashcode\u7ecf\u8fc7\u9ad8\u4f4e\u4f4d\u5f02\u6216\u4e4b\u540e\u7684\u503c\uff0c\u518d\u6309\u4f4d\u4e0e &amp;(table.lingth - 1),\u5f97\u5230\u4e00\u4e2a\u6570\u7ec4\u4e0b\u6807\uff0c\u7136\u540e\u6839\u636e\u8fd9\u4e2a\u6570\u7ec4\u4e0b\u6807\u5185\u7684\u72b6\u51b5\uff0c\u72b6\u51b5\u4e0d\u540c\uff0c\u7136\u540e\u60c5\u51b5\u4e5f\u4e0d\u540c\uff0c\u5927\u6982\u5206\u4e3a\u4e864\u79cd\u72b6\u6001\uff1a<\/p>\n<p>( 1.)\u7b2c\u4e00\u79cd\u5c31\u662f\u6570\u7ec4\u4e0b\u6807\u4e0b\u5185\u5bb9\u4e3a\u7a7a\uff1a<br \/>\n\u8fd9\u79cd\u60c5\u51b5\u6ca1\u4ec0\u4e48\u597d\u8bf4\u7684\uff0c\u4e3a\u7a7a\u636e\u76f4\u63a5\u5360\u6709\u8fd9\u4e2aslot\u69fd\u4f4d\u5c31\u597d\u4e86\uff0c\u7136\u540e\u628a\u5f53\u524d.put\u65b9\u6cd5\u4f20\u8fdb\u6765\u7684key\u548cvalue\u5305\u88c5\u6210\u4e00\u4e2anode\u5bf9\u8c61,\u653e\u5230\u8fd9\u4e2aslot\u4e2d\u5c31\u597d\u4e86\u3002<\/p>\n<p>( 2.)\u7b2c\u4e8c\u79cd\u60c5\u51b5\u5c31\u662f\u6570\u7ec4\u4e0b\u6807\u4e0b\u5185\u5bb9\u4e0d\u4e3a\u7a7a\uff0c\u4f46\u5b83\u5f15\u7528\u7684node\u8fd8\u6ca1\u6709\u94fe\u5316\uff1a<br \/>\n\u8fd9\u79cd\u60c5\u51b5\u4e0b\u5148\u8981\u5bf9\u6bd4\u4e00\u4e0b\u8fd9\u4e2anode\u5bf9\u8c61\u7684key\u4e0e\u5f53\u524dput\u5bf9\u8c61\u7684key\u662f\u5426\u5b8c\u5168.\u76f8\u7b49\uff0c\u5982\u679c\u5b8c\u5168\u76f8\u7b49\u7684\u60c5\u51b5\u4e0b\uff0c\u5c31\u884c\u8fdb\u884creplace\u64cd\u4f5c\uff0c\u628a\u4e4b\u524d\u7684\u69fd\u4f4d\u4e2dnode.\u4e0b\u7684value\u66ff\u6362\u6210\u65b0\u7684value\u5c31\u53ef\u4ee5\u4e86\uff0c\u5426\u5219\u7684\u8bdd\u8fd9\u4e2aput\u64cd\u4f5c\u5c31\u662f\u4e00\u4e2a\u6b63\u513f.\u516b\u7ecf\u7684hash\u51b2\u7a81,\u8fd9\u79cd\u60c5\u51b5\u5728slot\u69fd\u4f4d\u540e\u9762\u8ffd\u52a0\u4e00\u4e2anode\u5c31\u53ef\u4ee5\u4e86,\u7528\u5c3e\u63d2\u6cd5 ( \u524d\u9762\u8bb2\u8fc7\uff0cjdk7\u662f\u628a\u65b0\u589e\u5143\u7d20\u6dfb\u52a0\u5230\u5934\u90e8\u8282\u70b9\uff0c\u800cjdk8\u5219\u6dfb\u52a0\u5230\u5c3e\u90e8\u8282\u70b9)\u3002<\/p>\n<p>( 3.)\u7b2c\u4e09\u79cd\u5c31\u662f\u8be5\u6570\u7ec4\u4e0b\u6807\u4e0b\u5185\u5bb9\u5df2\u7ecf\u88ab\u94fe\u5316\u4e86\uff1a<br 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