{"id":1419,"date":"2026-05-06T09:01:27","date_gmt":"2026-05-06T01:01:27","guid":{"rendered":"https:\/\/yunyanglib.cn\/?p=1419"},"modified":"2026-05-06T09:01:28","modified_gmt":"2026-05-06T01:01:28","slug":"%e3%80%90java%e3%80%91hashmap-%e8%af%a6%e8%a7%a3%ef%bc%9a%e4%bb%8e%e5%ba%95%e5%b1%82%e5%8e%9f%e7%90%86%e5%88%b0%e5%ae%9e%e6%88%98%e5%ba%94%e7%94%a8","status":"publish","type":"post","link":"https:\/\/yunyanglib.cn\/?p=1419","title":{"rendered":"\u3010Java\u3011HashMap \u8be6\u89e3\uff1a\u4ece\u5e95\u5c42\u539f\u7406\u5230\u5b9e\u6218\u5e94\u7528"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">\u5927\u5bb6\u597d\uff0c\u6211\u662f\u4e91\u626c\uff5e \u4eca\u5929\u54b1\u4eec\u6df1\u5165\u804a\u804a Java \u4e2d\u6700\u5e38\u7528\u7684\u6570\u636e\u7ed3\u6784\u4e4b\u4e00 \u2014\u2014HashMap\u3002\u4f5c\u4e3a\u952e\u503c\u5bf9\u5b58\u50a8\u7684\u6838\u5fc3\u5de5\u5177\uff0cHashMap \u7684 O (1) \u67e5\u8be2\u6548\u7387\u3001\u7075\u6d3b\u7684\u6269\u5bb9\u673a\u5236\uff0c\u8ba9\u5b83\u6210\u4e3a\u7f13\u5b58\u3001\u7d22\u5f15\u3001\u6570\u636e\u7edf\u8ba1\u7b49\u573a\u666f\u7684\u9996\u9009\u3002\u8fd9\u7bc7\u6587\u7ae0\u4f1a\u4ece\u57fa\u7840\u4f7f\u7528\u3001\u5e95\u5c42\u539f\u7406\u3001\u6838\u5fc3\u673a\u5236\u5230\u5b9e\u6218\u573a\u666f\uff0c\u5e26\u5927\u5bb6\u5168\u9762\u5403\u900f HashMap\uff01<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e00\u3001HashMap \u57fa\u7840\uff1a\u589e\u5220\u6539\u67e5\u5168\u89e3\u6790<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">HashMap \u7684\u6838\u5fc3\u64cd\u4f5c\u975e\u5e38\u7b80\u6d01\uff0c\u54b1\u4eec\u7ed3\u5408\u4ee3\u7801\u793a\u4f8b\u4e00\u6b65\u6b65\u62c6\u89e3\uff1a<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u521d\u59cb\u5316<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u652f\u6301\u6307\u5b9a\u521d\u59cb\u5bb9\u91cf\u548c\u52a0\u8f7d\u56e0\u5b50\uff0c\u9ed8\u8ba4\u521d\u59cb\u5bb9\u91cf 16\uff0c\u52a0\u8f7d\u56e0\u5b50 0.75\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ 1. \u65e0\u53c2\u521d\u59cb\u5316\uff08\u9ed8\u8ba4\u5bb9\u91cf16\uff0c\u52a0\u8f7d\u56e0\u5b500.75\uff09\nHashMap&lt;String, Integer> userAgeMap = new HashMap&lt;>();\n\/\/ 2. \u6307\u5b9a\u521d\u59cb\u5bb9\u91cf\u548c\u52a0\u8f7d\u56e0\u5b50\nHashMap&lt;String, Integer> userInfoMap = new HashMap&lt;>(10, 0.75f);\n\/\/ 3. \u4ece\u5176\u4ed6Map\u521d\u59cb\u5316\nMap&lt;String, Integer> tempMap = new HashMap&lt;>();\ntempMap.put(\"Wangwu\", 25);\nHashMap&lt;String, Integer> copyMap = new HashMap&lt;>(tempMap);\n<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\">2. \u6dfb\u52a0\u5143\u7d20\uff08put ()\uff09<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u952e\u552f\u4e00\uff0c\u91cd\u590d\u6dfb\u52a0\u4f1a\u8986\u76d6\u539f\u6709\u503c\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>HashMap&lt;String, Integer> scoreMap = new HashMap&lt;>(); \/\/ \u57fa\u672c\u6dfb\u52a0\nscoreMap.put(\"Math\", 95);\nscoreMap.put(\"English\", 88);\nscoreMap.put(\"Java\", 92);\n\/\/ \u6279\u91cf\u6dfb\u52a0\uff08JDK8+\uff09\nscoreMap.putAll(Map.of(\"History\", 78, \"Physics\", 85));\n\/\/ putIfAbsent\uff1a\u952e\u4e0d\u5b58\u5728\u65f6\u624d\u6dfb\u52a0\uff08\u907f\u514d\u8986\u76d6\uff09\nscoreMap.putIfAbsent(\"Math\", 100); \/\/ \u4e0d\u4f1a\u751f\u6548\uff0cMath\u5df2\u5b58\u5728\nscoreMap.putIfAbsent(\"Chemistry\", 80); \/\/ \u65b0\u589e\u6210\u529f\n<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\">3. \u5220\u9664\u5143\u7d20\uff08remove ()\uff09<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u652f\u6301\u6839\u636e\u952e\u5220\u9664\uff0c\u6216\u952e\u503c\u5339\u914d\u5220\u9664\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ \u6839\u636e\u952e\u5220\u9664\nscoreMap.remove(\"History\");\n\n\/\/ \u952e\u503c\u5339\u914d\u5220\u9664\uff08\u4ec5\u5f53\u952e\u5b58\u5728\u4e14\u503c\u76f8\u7b49\u65f6\u5220\u9664\uff09\nscoreMap.remove(\"Physics\", 85); \/\/ \u751f\u6548\nscoreMap.remove(\"English\", 90); \/\/ \u4e0d\u751f\u6548\uff0cEnglish\u7684\u503c\u662f88\n<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\">4. \u4fee\u6539\u5143\u7d20\uff08put ()\/replace ()\uff09<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u4e24\u79cd\u65b9\u5f0f\uff1aput \u8986\u76d6\u6216 replace \u7cbe\u51c6\u4fee\u6539\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ put\u8986\u76d6\uff08\u901a\u7528\u65b9\u5f0f\uff09\nscoreMap.put(\"Java\", 98); \/\/ \u5c06Java\u6210\u7ee9\u4ece92\u6539\u4e3a98\n\n\/\/ replace\u7cbe\u51c6\u4fee\u6539\uff08\u4ec5\u5f53\u952e\u5b58\u5728\u65f6\u751f\u6548\uff09\nscoreMap.replace(\"English\", 88, 90); \/\/ \u6210\u529f\uff0c\u5c0688\u6539\u4e3a90\nscoreMap.replace(\"Chemistry\", 90); \/\/ \u76f4\u63a5\u4fee\u6539\u4e3a90\uff08\u65e0\u9700\u539f\u6570\u503c\uff09\nscoreMap.replace(\"Biology\", 70); \/\/ \u4e0d\u751f\u6548\uff0cBiology\u4e0d\u5b58\u5728\n<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\">5. \u67e5\u627e\u5143\u7d20\uff08get ()\/containsKey ()\uff09<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ \u83b7\u53d6\u952e\u5bf9\u5e94\u7684\u503c\uff08\u4e0d\u5b58\u5728\u8fd4\u56denull\uff09\nInteger mathScore = scoreMap.get(\"Math\");\nSystem.out.println(\"Math Score: \" + mathScore); \/\/ \u8f93\u51fa95\n\n\/\/ \u907f\u514dnull\uff1a\u4f7f\u7528getOrDefault\uff08\u4e0d\u5b58\u5728\u8fd4\u56de\u9ed8\u8ba4\u503c\uff09\nInteger biologyScore = scoreMap.getOrDefault(\"Biology\", 60);\nSystem.out.println(\"Biology Score: \" + biologyScore); \/\/ \u8f93\u51fa60\n\n\/\/ \u5224\u65ad\u952e\u662f\u5426\u5b58\u5728\nboolean hasEnglish = scoreMap.containsKey(\"English\");\nSystem.out.println(\"Has English Score: \" + hasEnglish); \/\/ \u8f93\u51fatrue\n\n\/\/ \u904d\u5386\u6240\u6709\u952e\u503c\u5bf9\uff08JDK8+\u6d41\u5f0f\u904d\u5386\uff09\nscoreMap.forEach((subject, score) -&gt; \n    System.out.printf(\"%s: %d%n\", subject, score)\n);\n<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e8c\u3001HashMap \u6838\u5fc3\u539f\u7406\uff1a\u6570\u7ec4 + \u94fe\u8868 \/ \u7ea2\u9ed1\u6811<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">HashMap \u7684\u9ad8\u6548\u6027\u6e90\u4e8e\u5176\u5e95\u5c42\u7ed3\u6784\uff0c\u54b1\u4eec\u7528\u901a\u4fd7\u7684\u8bed\u8a00\u62c6\u89e3\uff1a<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u5b58\u50a8\u7ed3\u6784<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u6570\u7ec4<\/strong>\uff1a\u6838\u5fc3\u5bb9\u5668\uff0c\u521d\u59cb\u5927\u5c0f 16\uff082 \u7684 4 \u6b21\u65b9\uff09\uff0c\u6bcf\u4e2a\u4f4d\u7f6e\u79f0\u4e3a &#8220;\u6876\uff08bucket\uff09&#8221;<\/li>\n\n\n\n<li><strong>\u94fe\u8868<\/strong>\uff1a\u89e3\u51b3\u54c8\u5e0c\u51b2\u7a81\uff08\u4e0d\u540c\u952e\u8ba1\u7b97\u51fa\u540c\u4e00\u6876\u4f4d\uff09\uff0cJDK8 \u524d\u94fe\u8868\u91c7\u7528\u5934\u63d2\u6cd5\uff0cJDK8 \u540e\u6539\u4e3a\u5c3e\u63d2\u6cd5<\/li>\n\n\n\n<li><strong>\u7ea2\u9ed1\u6811<\/strong>\uff1a\u5f53\u94fe\u8868\u957f\u5ea6\u8d85\u8fc7\u9608\u503c\uff08\u9ed8\u8ba4 8\uff09\uff0c\u4e14\u6570\u7ec4\u5bb9\u91cf\u226564 \u65f6\uff0c\u94fe\u8868\u8f6c\u4e3a\u7ea2\u9ed1\u6811\uff08\u67e5\u8be2\u65f6\u95f4\u590d\u6742\u5ea6\u4ece O (n) \u964d\u4e3a O (logn)\uff09<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">2. \u54c8\u5e0c\u8ba1\u7b97\u4e0e\u6876\u4f4d\u5b9a\u4f4d<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>hash () \u65b9\u6cd5<\/strong>\uff1a\u5c06\u952e\u7684 hashCode \u9ad8\u4f4d\u4e0e\u4f4e\u4f4d\u5f02\u6216\uff0c\u589e\u52a0\u968f\u673a\u6027\uff1a<\/li>\n<\/ol>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ JDK8 hash()\u6e90\u7801\u7b80\u5316\nstatic final int hash(Object key) {\n    int h;\n    \/\/ key\u4e3anull\u65f6hash=0\uff0c\u5426\u5219h = key.hashCode() ^ (h &gt;&gt;&gt; 16)\n    return (key == null) ? 0 : (h = key.hashCode()) ^ (h &gt;&gt;&gt; 16);\n}\n<\/code><\/pre>\n\n\n\n<ol start=\"2\" class=\"wp-block-list\">\n<li><strong>\u6876\u4f4d\u8ba1\u7b97<\/strong>\uff1a\u901a\u8fc7 <code>(\u6570\u7ec4\u957f\u5ea6-1) &amp; hash<\/code> \u786e\u5b9a\u6876\u4f4d\uff08\u7b49\u4ef7\u4e8e\u53d6\u6a21\uff0c\u4f46\u6548\u7387\u66f4\u9ad8\uff09\uff1a<\/li>\n<\/ol>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ \u793a\u4f8b\uff1a\u6570\u7ec4\u957f\u5ea616\uff08\u4e8c\u8fdb\u523610000\uff09\uff0c\u6570\u7ec4\u957f\u5ea6-1=15\uff08\u4e8c\u8fdb\u523601111\uff09\nString key = \"Java\";\nint hash = key.hashCode() ^ (key.hashCode() &gt;&gt;&gt; 16);\nint bucketIndex = (16 - 1) &amp; hash; \/\/ \u8ba1\u7b97\u7ed3\u679c\u4e3a0-15\u4e4b\u95f4\u7684\u6574\u6570\n<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e09\u3001\u5173\u952e\u673a\u5236\uff1a\u6269\u5bb9\u4e0e\u52a0\u8f7d\u56e0\u5b50<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u4e3a\u4ec0\u4e48\u9700\u8981\u6269\u5bb9\uff1f<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u6570\u7ec4\u5bb9\u91cf\u56fa\u5b9a\uff0c\u5f53\u5143\u7d20\u6570\u91cf\u8d85\u8fc7\u300c\u9608\u503c\uff08\u5bb9\u91cf \u00d7 \u52a0\u8f7d\u56e0\u5b50\uff09\u300d\u65f6\uff0c\u4f1a\u89e6\u53d1\u6269\u5bb9\uff08\u9ed8\u8ba4\u5bb9\u91cf 16\uff0c\u9608\u503c 12\uff09\uff0c\u907f\u514d\u6876\u5185\u94fe\u8868 \/ \u7ea2\u9ed1\u6811\u8fc7\u957f\u5bfc\u81f4\u67e5\u8be2\u6548\u7387\u4e0b\u964d\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2. \u6269\u5bb9\u6d41\u7a0b\uff08JDK8\uff09<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>\u65b0\u5bb9\u91cf = \u539f\u5bb9\u91cf \u00d7 2\uff08\u59cb\u7ec8\u4fdd\u6301 2 \u7684\u5e42\u6b21\u65b9\uff09<\/li>\n\n\n\n<li>\u91cd\u65b0\u8ba1\u7b97\u6240\u6709\u5143\u7d20\u7684 hash \u503c\u548c\u6876\u4f4d<\/li>\n\n\n\n<li>\u5c06\u5143\u7d20\u8fc1\u79fb\u5230\u65b0\u6570\u7ec4\uff08\u94fe\u8868\u8282\u70b9\u65e0\u9700\u91cd\u65b0\u8ba1\u7b97 hash\uff0c\u901a\u8fc7\u9ad8\u4f4d\u5224\u65ad\u6876\u4f4d\uff09<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\">3. \u52a0\u8f7d\u56e0\u5b50\u4e3a\u4ec0\u4e48\u662f 0.75\uff1f<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u52a0\u8f7d\u56e0\u5b50\u592a\u5c0f\uff08\u5982 0.5\uff09\uff1a\u7a7a\u95f4\u5229\u7528\u7387\u4f4e\uff0c\u9891\u7e41\u6269\u5bb9<\/li>\n\n\n\n<li>\u52a0\u8f7d\u56e0\u5b50\u592a\u5927\uff08\u5982 0.9\uff09\uff1a\u54c8\u5e0c\u51b2\u7a81\u6982\u7387\u5267\u589e\uff0cCPU \u7f13\u5b58\u547d\u4e2d\u7387\u4e0b\u964d<\/li>\n\n\n\n<li>0.75 \u662f\u65f6\u95f4\u4e0e\u7a7a\u95f4\u7684\u5e73\u8861\u70b9\uff0c\u57fa\u4e8e\u6cca\u677e\u5206\u5e03\uff0c\u6b64\u65f6\u6876\u5185\u5143\u7d20\u4e2a\u6570\u4e3a 8 \u7684\u6982\u7387\u6781\u4f4e\uff08\u7ea6 0.0000001\uff09\uff0c\u9002\u5408\u89e6\u53d1\u94fe\u8868\u8f6c\u7ea2\u9ed1\u6811<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">\u56db\u3001\u5b9e\u6218\u573a\u666f\uff1aHashMap \u7684 3 \u4e2a\u7ecf\u5178\u7528\u6cd5<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u7f13\u5b58\u7528\u6237\u4fe1\u606f<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ \u6a21\u62df\u7f13\u5b58\u7528\u6237\u4fe1\u606f\uff08\u952e\uff1a\u7528\u6237ID\uff0c\u503c\uff1aUser\u5bf9\u8c61\uff09\n@Data\n@AllArgsConstructor\n@NoArgsConstructor\npublic class User {\n\n    private String id;\n    private String name;\n    private int age;\n}\n\nHashMap&lt;String, User> userCache = new HashMap&lt;>(); \/\/ \u7f13\u5b58\u7528\u6237\nuserCache.put(\"U1001\", new User(\"U1001\", \"Zhangsan\", 18));\nuserCache.put(\"U1002\", new User(\"U1002\", \"Lisi\", 20));\n\/\/ \u5feb\u901f\u67e5\u8be2\u7528\u6237\nUser user = userCache.get(\"U1001\");\nif (user != null) {\n    System.out.println(\"User Name: \" + user.getName());\n}\n<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\">2. \u7edf\u8ba1\u5355\u8bcd\u51fa\u73b0\u9891\u7387<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>String text = \"Java is good Java is powerful Java is easy to learn\";\nString&#91;] words = text.split(\" \");\nHashMap&lt;String, Integer> wordCount = new HashMap&lt;>();\nHashMap&lt;String, Integer> wordCount2 = new HashMap&lt;>();\nfor (String word : words) {\n    \/\/ \u65b9\u5f0f1\uff1a\u4f20\u7edf\u5199\u6cd5\n    if (wordCount.containsKey(word)) {\n        wordCount.put(word, wordCount.get(word) + 1);\n    } else {\n        wordCount.put(word, 1);\n    }\n}\nArrays.stream(words).forEach(word -> {\n    \/\/ \u65b9\u5f0f2\uff1a\u7b80\u5316\u5199\u6cd5\uff08JDK8+\uff09\n    wordCount2.put(word, wordCount2.getOrDefault(word, 0) + 1);\n});\n\/\/ \u8f93\u51fa\u7edf\u8ba1\u7ed3\u679c\nwordCount.forEach((word, count) ->\n        System.out.printf(\"wordCount:%s: %d\u6b21%n\", word, count)\n);\nwordCount2.forEach((word, count) -> {\n    System.out.printf(\"wordCount2:%s: %d\u6b21%n\", word, count);\n});\n<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\">3. \u6784\u5efa\u6587\u6863\u7d22\u5f15<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ \u952e\uff1a\u5173\u952e\u8bcd\uff0c\u503c\uff1a\u5305\u542b\u8be5\u5173\u952e\u8bcd\u7684\u6587\u6863ID\u5217\u8868\nHashMap&lt;String, List&lt;String>> docIndex = new HashMap&lt;>();\n\/\/ \u7ed9\u6587\u6863ID\u4e3aD1\u7684\u6587\u6863\u6dfb\u52a0\u5173\u952e\u8bcd\ndocIndex.computeIfAbsent(\"Java\", k -> new ArrayList&lt;>()).add(\"D1\");\ndocIndex.computeIfAbsent(\"HashMap\", k -> new ArrayList&lt;>()).add(\"D1\");\n\/\/ \u7ed9\u6587\u6863ID\u4e3aD2\u7684\u6587\u6863\u6dfb\u52a0\u5173\u952e\u8bcd\ndocIndex.computeIfAbsent(\"Java\", k -> new ArrayList&lt;>()).add(\"D2\");\ndocIndex.computeIfAbsent(\"ConcurrentHashMap\", k -> new ArrayList&lt;>()).add(\"D2\");\n\/\/ \u67e5\u8be2\u5305\u542b\"Java\"\u7684\u6587\u6863\nList&lt;String> javaDocs = docIndex.getOrDefault(\"Java\", Collections.emptyList());\nSystem.out.println(\"\u5305\u542bJava\u7684\u6587\u6863\uff1a\" + javaDocs); \/\/ \u8f93\u51fa&#91;D1, D2]\n<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e94\u3001\u907f\u5751\u6307\u5357\uff1a\u7ebf\u7a0b\u5b89\u5168\u4e0e\u6ce8\u610f\u4e8b\u9879<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u7ebf\u7a0b\u4e0d\u5b89\u5168\u7684\u95ee\u9898<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u591a\u7ebf\u7a0b\u6269\u5bb9\u53ef\u80fd\u5bfc\u81f4\u6b7b\u5faa\u73af\uff08JDK7\uff09<\/li>\n\n\n\n<li>\u5e76\u53d1 put \u53ef\u80fd\u5bfc\u81f4\u5143\u7d20\u4e22\u5931<\/li>\n\n\n\n<li>\u5e76\u53d1 put\/get \u53ef\u80fd\u83b7\u53d6\u5230 null \u503c<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">2. \u7ebf\u7a0b\u5b89\u5168\u89e3\u51b3\u65b9\u6848<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ \u65b9\u68481\uff1a\u4f7f\u7528ConcurrentHashMap\uff08\u63a8\u8350\uff0c\u9ad8\u6548\u7ebf\u7a0b\u5b89\u5168\uff09\nConcurrentHashMap&lt;String, Integer> concurrentHashMap = new ConcurrentHashMap&lt;>();\n\/\/ \u65b9\u68482\uff1a\u4f7f\u7528Collections.synchronizedMap\uff08\u7b80\u5355\u4f46\u6548\u7387\u4f4e\uff09\nMap&lt;String,Integer> syncMap = Collections.synchronizedMap(new HashMap&lt;>());<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\">3. \u5176\u4ed6\u6ce8\u610f\u4e8b\u9879<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u952e\u4e0d\u80fd\u4e3anull\uff08\u9664\u975e\u660e\u786e\u5141\u8bb8\uff0c\u5efa\u8bae\u907f\u514d\uff09<\/li>\n\n\n\n<li>\u904d\u5386\u65e0\u5e8f\uff08\u9700\u6709\u5e8f\u8bf7\u4f7f\u7528TreeMap\uff09<\/li>\n\n\n\n<li>\u4e0d\u8981\u5728\u904d\u5386\u8fc7\u7a0b\u4e2d\u4fee\u6539Map\uff08\u63a8\u8350\u4f7f\u7528\u8fed\u4ee3\u5668\u7684remove()\u65b9\u6cd5\uff09<br><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">\u603b\u7ed3<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">HashMap\u4f5c\u4e3aJava\u96c6\u5408\u6846\u67b6\u7684\u6838\u5fc3\uff0c\u5176\u300c\u6570\u7ec4+\u94fe\u8868\/\u7ea2\u9ed1\u6811\u300d\u7684\u5b58\u50a8\u7ed3\u6784\u3001\u9ad8\u6548\u7684\u54c8\u5e0c\u8ba1\u7b97\u3001\u52a8\u6001\u6269\u5bb9\u673a\u5236\uff0c\u4f7f\u5176\u5728\u7edd\u5927\u591a\u6570\u573a\u666f\u4e0b\u90fd\u80fd\u63d0\u4f9bO(1)\u7684\u64cd\u4f5c\u6548\u7387\u3002\u638c\u63e1\u5b83\u7684\u5e95\u5c42\u539f\u7406\u548c\u5b9e\u6218\u6280\u5de7\uff0c\u80fd\u8ba9\u4f60\u7684\u4ee3\u7801\u66f4\u9ad8\u6548\u3001\u66f4\u7a33\u5065\uff5e<br><br>\u5982\u679c\u8fd9\u7bc7\u6587\u7ae0\u5bf9\u4f60\u6709\u5e2e\u52a9\uff0c\u6b22\u8fce\u70b9\u8d5e\u3001\u7559\u8a00\u4ea4\u6d41\uff01\u4e0b\u671f\u54b1\u4eec\u804a\u804aHashMap\u7684&#8221;\u5144\u5f1f&#8221;\u2014\u2014ConcurrentHashMap\uff0c\u770b\u770b\u5b83\u662f\u5982\u4f55\u89e3\u51b3\u7ebf\u7a0b\u5b89\u5168\u95ee\u9898\u7684\uff5e<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5927\u5bb6\u597d\uff0c\u6211\u662f\u4e91\u626c\uff5e \u4eca\u5929\u54b1\u4eec\u6df1\u5165\u804a\u804a Java \u4e2d\u6700\u5e38\u7528\u7684\u6570\u636e\u7ed3\u6784\u4e4b\u4e00 \u2014\u2014HashMap\u3002\u4f5c\u4e3a\u952e\u503c\u5bf9\u5b58\u50a8\u7684\u6838<\/p>\n<div class=\"more-link\">\n\t\t\t\t <a href=\"https:\/\/yunyanglib.cn\/?p=1419\" class=\"link-btn theme-btn\"><span>Read More <\/span> <i class=\"fa fa-caret-right\"><\/i><\/a>\n\t\t\t<\/div>\n","protected":false},"author":1,"featured_media":1421,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[20],"tags":[15],"class_list":["post-1419","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-java","tag-java"],"_links":{"self":[{"href":"https:\/\/yunyanglib.cn\/index.php?rest_route=\/wp\/v2\/posts\/1419","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/yunyanglib.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/yunyanglib.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/yunyanglib.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/yunyanglib.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1419"}],"version-history":[{"count":2,"href":"https:\/\/yunyanglib.cn\/index.php?rest_route=\/wp\/v2\/posts\/1419\/revisions"}],"predecessor-version":[{"id":1422,"href":"https:\/\/yunyanglib.cn\/index.php?rest_route=\/wp\/v2\/posts\/1419\/revisions\/1422"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/yunyanglib.cn\/index.php?rest_route=\/wp\/v2\/media\/1421"}],"wp:attachment":[{"href":"https:\/\/yunyanglib.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1419"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/yunyanglib.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1419"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/yunyanglib.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1419"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}