{"id":619,"date":"2024-11-08T12:33:20","date_gmt":"2024-11-08T04:33:20","guid":{"rendered":"https:\/\/www.ikaros.love\/?p=619"},"modified":"2024-11-08T12:33:20","modified_gmt":"2024-11-08T04:33:20","slug":"java-hashcode-%e8%a7%a3%e6%9e%90","status":"publish","type":"post","link":"https:\/\/www.ikaros.love\/?p=619","title":{"rendered":"java hashcode \u89e3\u6790"},"content":{"rendered":"\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" width=\"425\" height=\"425\" src=\"https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/47.png\" alt=\"\" class=\"wp-image-620\" srcset=\"https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/47.png 425w, https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/47-300x300.png 300w, https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/47-150x150.png 150w, https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/47-200x200.png 200w\" sizes=\"(max-width: 425px) 100vw, 425px\" \/><\/figure>\n\n\n\n<p>\u642c\u8fd0\u81ea<\/p>\n\n\n\n<p><a href=\"https:\/\/javabetter.cn\/basic-extra-meal\/hashcode.html\">Java hashCode\u65b9\u6cd5\u6df1\u5165\u89e3\u6790 | \u4e8c\u54e5\u7684Java\u8fdb\u9636\u4e4b\u8def<\/a><\/p>\n\n\n\n<p>\u4eca\u5929\u6211\u4eec\u6765\u8c08\u8c08 Java \u4e2d\u7684&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u3002\u4f17\u6240\u5468\u77e5\uff0cJava \u662f\u4e00\u95e8\u9762\u5411\u5bf9\u8c61\u7684\u7f16\u7a0b\u8bed\u8a00\uff0c\u6240\u6709\u7684\u7c7b\u90fd\u4f1a\u9ed8\u8ba4\u7ee7\u627f\u81ea Object \u7c7b\uff0c\u800c Object \u7684\u4e2d\u6587\u610f\u601d\u5c31\u662f\u201c\u5bf9\u8c61\u201d\u3002<\/p>\n\n\n\n<p>Object \u7c7b\u4e2d\u5c31\u5305\u542b\u4e86&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>public native int hashCode();<\/code><\/pre>\n\n\n\n<p>\u610f\u5473\u7740\u6240\u6709\u7684\u7c7b\u90fd\u4f1a\u6709\u4e00\u4e2a&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\uff0c\u8be5\u65b9\u6cd5\u4f1a\u8fd4\u56de\u4e00\u4e2a int \u7c7b\u578b\u7684\u503c\u3002\u7531\u4e8e&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u662f\u4e00\u4e2a<a href=\"https:\/\/javabetter.cn\/oo\/native-method.html\" target=\"_blank\" rel=\"noreferrer noopener\">\u672c\u5730\u65b9\u6cd5<\/a>\uff08<code>native<\/code>&nbsp;\u5173\u952e\u5b57\u4fee\u9970\u7684\u65b9\u6cd5\uff0c\u7528&nbsp;<code>C\/C++<\/code>&nbsp;\u8bed\u8a00\u5b9e\u73b0\uff0c\u7531 Java \u8c03\u7528\uff09\uff0c\u610f\u5473\u7740 Object \u7c7b\u4e2d\u5e76\u6ca1\u6709\u7ed9\u51fa\u5177\u4f53\u7684\u5b9e\u73b0\u3002<\/p>\n\n\n\n<p>\u5177\u4f53\u7684\u5b9e\u73b0\u53ef\u4ee5\u53c2\u8003\u00a0<code>jdk\/src\/hotspot\/share\/runtime\/synchronizer.cpp<\/code>\uff08\u6e90\u7801\u53ef\u4ee5\u5230\u00a0<a href=\"https:\/\/github.com\/openjdk\/jdk\/blob\/master\/src\/hotspot\/share\/runtime\/synchronizer.cpp\" target=\"_blank\" rel=\"noreferrer noopener\">GitHub \u4e0a OpenJDK \u7684\u4ed3\u5e93\u4e2d\u4e0b\u8f7d<\/a>\uff09\u3002<code>get_next_hash()<\/code>\u00a0\u65b9\u6cd5\u4f1a\u6839\u636e hashCode \u7684\u53d6\u503c\u6765\u51b3\u5b9a\u91c7\u7528\u54ea\u4e00\u79cd\u54c8\u5e0c\u503c\u7684\u751f\u6210\u7b56\u7565\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"1024\" height=\"712\" src=\"https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/image-25-1024x712.png\" alt=\"\" class=\"wp-image-621\" srcset=\"https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/image-25-1024x712.png 1024w, https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/image-25-300x209.png 300w, https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/image-25-768x534.png 768w, https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/image-25-670x466.png 670w, https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/image-25.png 1077w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p>Java 9 \u4e4b\u540e\uff0c<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u4f1a\u88ab&nbsp;<code>@HotSpotIntrinsicCandidate<\/code>&nbsp;\u6ce8\u89e3\u4fee\u9970\uff0c\u8868\u660e\u5b83\u5728 HotSpot \u865a\u62df\u673a\u4e2d\u6709\u4e00\u5957\u9ad8\u6548\u7684\u5b9e\u73b0\uff0c\u57fa\u4e8e CPU \u6307\u4ee4\u3002<\/p>\n\n\n\n<p>\u90a3\u5927\u5bb6\u6709\u6ca1\u6709\u60f3\u8fc7\u8fd9\u6837\u4e00\u4e2a\u95ee\u9898\uff1a<strong>\u4e3a\u4ec0\u4e48 Object \u7c7b\u9700\u8981\u4e00\u4e2a&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u5462<\/strong>\uff1f<\/p>\n\n\n\n<p>\u5728 Java \u4e2d\uff0c<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u7684\u4e3b\u8981\u4f5c\u7528\u5c31\u662f\u4e3a\u4e86\u914d\u5408<a href=\"https:\/\/javabetter.cn\/collection\/hashmap.html\" target=\"_blank\" rel=\"noreferrer noopener\">\u54c8\u5e0c\u8868<\/a>\u4f7f\u7528\u7684\u3002<\/p>\n\n\n\n<p>\u54c8\u5e0c\u8868\uff08Hash Table\uff09\uff0c\u4e5f\u53eb\u6563\u5217\u8868\uff0c\u662f\u4e00\u79cd\u53ef\u4ee5\u901a\u8fc7\u5173\u952e\u7801\u503c\uff08key-value\uff09\u76f4\u63a5\u8bbf\u95ee\u7684\u6570\u636e\u7ed3\u6784\uff0c\u5b83\u6700\u5927\u7684\u7279\u70b9\u5c31\u662f\u53ef\u4ee5\u5feb\u901f\u5b9e\u73b0\u67e5\u627e\u3001\u63d2\u5165\u548c\u5220\u9664\u3002\u5176\u4e2d\u7528\u5230\u7684\u7b97\u6cd5\u53eb\u505a\u54c8\u5e0c\uff0c\u5c31\u662f\u628a\u4efb\u610f\u957f\u5ea6\u7684\u8f93\u5165\uff0c\u53d8\u6362\u6210\u56fa\u5b9a\u957f\u5ea6\u7684\u8f93\u51fa\uff0c\u8be5\u8f93\u51fa\u5c31\u662f\u54c8\u5e0c\u503c\u3002\u50cf MD5\u3001SHA1 \u90fd\u7528\u7684\u662f\u54c8\u5e0c\u7b97\u6cd5\u3002<\/p>\n\n\n\n<p>\u50cf Java \u4e2d\u7684 HashSet\u3001Hashtable\uff08\u6ce8\u610f\u662f\u5c0f\u5199\u7684 t\uff09\u3001HashMap \u90fd\u662f\u57fa\u4e8e\u54c8\u5e0c\u8868\u7684\u5177\u4f53\u5b9e\u73b0\u3002\u5176\u4e2d\u7684&nbsp;<a href=\"https:\/\/javabetter.cn\/collection\/hashmap.html\" target=\"_blank\" rel=\"noreferrer noopener\">HashMap<\/a>&nbsp;\u5c31\u662f\u6700\u5178\u578b\u7684\u4ee3\u8868\uff0c\u4e0d\u4ec5\u9762\u8bd5\u5b98\u7ecf\u5e38\u95ee\uff0c\u5de5\u4f5c\u4e2d\u7684\u4f7f\u7528\u9891\u7387\u4e5f\u975e\u5e38\u7684\u9ad8\u3002<\/p>\n\n\n\n<p>\u5927\u5bb6\u60f3\u4e00\u4e0b\uff0c\u5982\u679c\u6ca1\u6709\u54c8\u5e0c\u8868\uff0c\u4f46\u53c8\u9700\u8981\u8fd9\u6837\u4e00\u4e2a\u6570\u636e\u7ed3\u6784\uff0c\u5b83\u91cc\u9762\u5b58\u653e\u7684\u6570\u636e\u662f\u4e0d\u5141\u8bb8\u91cd\u590d\u7684\uff0c\u8be5\u600e\u4e48\u529e\u5462\uff1f<\/p>\n\n\n\n<p>\u8981\u4e0d\u4f7f\u7528&nbsp;<code>equals()<\/code>&nbsp;\u65b9\u6cd5\u8fdb\u884c\u9010\u4e2a\u6bd4\u8f83\uff1f\u8fd9\u79cd\u65b9\u6848\u5f53\u7136\u662f\u53ef\u884c\u7684\u3002\u4f46\u5982\u679c\u6570\u636e\u91cf\u7279\u522b\u7279\u522b\u5927\uff0c\u91c7\u7528&nbsp;<code>equals()<\/code>&nbsp;\u65b9\u6cd5\u8fdb\u884c\u9010\u4e2a\u5bf9\u6bd4\u7684\u6548\u7387\u80af\u5b9a\u5f88\u4f4e\u5f88\u4f4e\uff0c\u6700\u597d\u7684\u89e3\u51b3\u65b9\u6848\u5c31\u662f\u54c8\u5e0c\u8868\u3002<\/p>\n\n\n\n<p>\u62ff HashMap \u6765\u8bf4\u5427\u3002\u5f53\u6211\u4eec\u8981\u5728\u5b83\u91cc\u9762\u6dfb\u52a0\u5bf9\u8c61\u65f6\uff0c\u5148\u8c03\u7528\u8fd9\u4e2a\u5bf9\u8c61\u7684&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\uff0c\u5f97\u5230\u5bf9\u5e94\u7684\u54c8\u5e0c\u503c\uff0c\u7136\u540e\u5c06\u54c8\u5e0c\u503c\u548c\u5bf9\u8c61\u4e00\u8d77\u653e\u5230 HashMap \u4e2d\u3002\u5f53\u6211\u4eec\u8981\u518d\u6dfb\u52a0\u4e00\u4e2a\u65b0\u7684\u5bf9\u8c61\u65f6\uff1a<\/p>\n\n\n\n<ul>\n<li>\u83b7\u53d6\u5bf9\u8c61\u7684\u54c8\u5e0c\u503c\uff1b<\/li>\n\n\n\n<li>\u548c\u4e4b\u524d\u5df2\u7ecf\u5b58\u5728\u7684\u54c8\u5e0c\u503c\u8fdb\u884c\u6bd4\u8f83\uff0c\u5982\u679c\u4e0d\u76f8\u7b49\uff0c\u76f4\u63a5\u5b58\u8fdb\u53bb\uff1b<\/li>\n\n\n\n<li>\u5982\u679c\u6709\u76f8\u7b49\u7684\uff0c\u518d\u8c03\u7528&nbsp;<code>equals()<\/code>&nbsp;\u65b9\u6cd5\u8fdb\u884c\u5bf9\u8c61\u4e4b\u95f4\u7684\u6bd4\u8f83\uff0c\u5982\u679c\u76f8\u7b49\uff0c\u4e0d\u5b58\u4e86\uff1b<\/li>\n\n\n\n<li>\u5982\u679c\u4e0d\u7b49\uff0c\u8bf4\u660e\u54c8\u5e0c\u51b2\u7a81\u4e86\uff0c\u589e\u52a0\u4e00\u4e2a\u94fe\u8868\uff0c\u5b58\u653e\u65b0\u7684\u5bf9\u8c61\uff1b<\/li>\n\n\n\n<li>\u5982\u679c\u94fe\u8868\u7684\u957f\u5ea6\u5927\u4e8e 8\uff0c\u8f6c\u4e3a\u7ea2\u9ed1\u6811\u6765\u5904\u7406\u3002<\/li>\n<\/ul>\n\n\n\n<p>\u5c31\u8fd9\u4e48\u4e00\u5957\u4e0b\u6765\uff0c\u8c03\u7528&nbsp;<code>equals()<\/code>&nbsp;\u65b9\u6cd5\u7684\u9891\u7387\u5c31\u5927\u5927\u964d\u4f4e\u4e86\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u53ea\u8981\u54c8\u5e0c\u7b97\u6cd5\u8db3\u591f\u7684\u9ad8\u6548\uff0c\u628a\u53d1\u751f\u54c8\u5e0c\u51b2\u7a81\u7684\u9891\u7387\u964d\u5230\u6700\u4f4e\uff0c\u54c8\u5e0c\u8868\u7684\u6548\u7387\u5c31\u7279\u522b\u7684\u9ad8\u3002<\/p>\n\n\n\n<p>\u6765\u770b\u4e00\u4e0b HashMap \u7684\u54c8\u5e0c\u7b97\u6cd5\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>static final int hash(Object key) {\n    int h;\n    return (key == null) ? 0 : (h = key.hashCode()) ^ (h &gt;&gt;&gt; 16);\n}<\/code><\/pre>\n\n\n\n<p>\u5148\u8c03\u7528\u5bf9\u8c61\u7684&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\uff0c\u7136\u540e\u5bf9\u8be5\u503c\u8fdb\u884c\u53f3\u79fb\u8fd0\u7b97\uff0c\u7136\u540e\u518d\u8fdb\u884c\u5f02\u6216\u8fd0\u7b97\u3002<\/p>\n\n\n\n<p>\u901a\u5e38\u6765\u8bf4\uff0cString \u4f1a\u7528\u6765\u4f5c\u4e3a HashMap \u7684\u952e\u8fdb\u884c\u54c8\u5e0c\u8fd0\u7b97\uff0c\u56e0\u6b64\u6211\u4eec\u518d\u6765\u770b\u4e00\u4e0b String \u7684&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>public int hashCode() {\n    int h = hash;\n    if (h == 0 &amp;&amp; value.length &gt; 0) {\n        char val&#91;] = value;\n\n        for (int i = 0; i &lt; value.length; i++) {\n            h = 31 * h + val&#91;i];\n        }\n        hash = h;\n    }\n    return h;\n}<\/code><\/pre>\n\n\n\n<p>\u53ef\u60f3\u800c\u77e5\uff0c\u7ecf\u8fc7\u8fd9\u4e48\u4e00\u7cfb\u5217\u590d\u6742\u7684\u8fd0\u7b97\uff0c\u518d\u52a0\u4e0a JDK \u4f5c\u8005\u8fd9\u79cd\u5927\u5e08\u7ea7\u522b\u7684\u8bbe\u8ba1\uff0c\u54c8\u5e0c\u51b2\u7a81\u7684\u6982\u7387\u6211\u76f8\u4fe1\u5df2\u7ecf\u964d\u5230\u4e86\u6700\u4f4e\uff08\u6211\u4eec\u5728 HashMap \u4e2d\u6df1\u5165\u63a2\u8ba8\u8fc7\uff09\u3002<\/p>\n\n\n\n<p>\u5f53\u7136\u4e86\uff0c\u4ece\u7406\u8bba\u4e0a\u6765\u8bf4\uff0c\u5bf9\u4e8e\u4e24\u4e2a\u4e0d\u540c\u5bf9\u8c61\uff0c\u5b83\u4eec\u901a\u8fc7&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u8ba1\u7b97\u540e\u7684\u503c\u53ef\u80fd\u76f8\u540c\u3002\u56e0\u6b64\uff0c\u4e0d\u80fd\u4f7f\u7528&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u6765\u5224\u65ad\u4e24\u4e2a\u5bf9\u8c61\u662f\u5426\u76f8\u7b49\uff0c\u5fc5\u987b\u5f97\u901a\u8fc7&nbsp;<code>equals()<\/code>&nbsp;\u65b9\u6cd5\u3002<\/p>\n\n\n\n<p>\u4e5f\u5c31\u662f\u8bf4\uff1a<\/p>\n\n\n\n<ul>\n<li>\u5982\u679c\u4e24\u4e2a\u5bf9\u8c61\u8c03\u7528&nbsp;<code>equals()<\/code>&nbsp;\u65b9\u6cd5\u5f97\u5230\u7684\u7ed3\u679c\u4e3a true\uff0c\u8c03\u7528&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u5f97\u5230\u7684\u7ed3\u679c\u5fc5\u5b9a\u76f8\u7b49\uff1b<\/li>\n\n\n\n<li>\u5982\u679c\u4e24\u4e2a\u5bf9\u8c61\u8c03\u7528&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u5f97\u5230\u7684\u7ed3\u679c\u4e0d\u76f8\u7b49\uff0c\u8c03\u7528&nbsp;<code>equals()<\/code>&nbsp;\u65b9\u6cd5\u5f97\u5230\u7684\u7ed3\u679c\u5fc5\u5b9a\u4e3a false\uff1b<\/li>\n<\/ul>\n\n\n\n<p>\u53cd\u4e4b\uff1a<\/p>\n\n\n\n<ul>\n<li>\u5982\u679c\u4e24\u4e2a\u5bf9\u8c61\u8c03\u7528&nbsp;<code>equals()<\/code>&nbsp;\u65b9\u6cd5\u5f97\u5230\u7684\u7ed3\u679c\u4e3a false\uff0c\u8c03\u7528&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u5f97\u5230\u7684\u7ed3\u679c\u4e0d\u4e00\u5b9a\u4e0d\u76f8\u7b49\uff1b<\/li>\n\n\n\n<li>\u5982\u679c\u4e24\u4e2a\u5bf9\u8c61\u8c03\u7528&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u5f97\u5230\u7684\u7ed3\u679c\u76f8\u7b49\uff0c\u8c03\u7528&nbsp;<code>equals()<\/code>&nbsp;\u65b9\u6cd5\u5f97\u5230\u7684\u7ed3\u679c\u4e0d\u4e00\u5b9a\u4e3a true\uff1b<\/li>\n<\/ul>\n\n\n\n<p>\u6765\u770b\u4e0b\u9762\u8fd9\u6bb5\u4ee3\u7801\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>public class Test {\n    public static void main(String&#91;] args) {\n        Student s1 = new Student(18, \"\u5f20\u4e09\");\n        Map&lt;Student, Integer&gt; scores = new HashMap&lt;&gt;();\n        scores.put(s1, 98);\n        System.out.println(scores.get(new Student(18, \"\u5f20\u4e09\")));\n    }\n}\n class Student {\n    private int age;\n    private String name;\n\n     public Student(int age, String name) {\n         this.age = age;\n         this.name = name;\n     }\n\n     @Override\n     public boolean equals(Object o) {\n         Student student = (Student) o;\n         return age == student.age &amp;&amp;\n                 Objects.equals(name, student.name);\n     }\n }<\/code><\/pre>\n\n\n\n<p>\u6211\u4eec\u91cd\u5199\u4e86 Student \u7c7b\u7684&nbsp;<code>equals()<\/code>&nbsp;\u65b9\u6cd5\uff0c\u5982\u679c\u4e24\u4e2a\u5b66\u751f\u7684\u5e74\u7eaa\u548c\u59d3\u540d\u76f8\u540c\uff0c\u6211\u4eec\u5c31\u8ba4\u4e3a\u662f\u540c\u4e00\u4e2a\u5b66\u751f\uff0c\u867d\u7136\u5f88\u79bb\u8c31\uff0c\u4f46\u6211\u4eec\u5c31\u662f\u8fd9\u4e48\u8349\u7387\u3002<\/p>\n\n\n\n<p>\u5728&nbsp;<code>main()<\/code>&nbsp;\u65b9\u6cd5\u4e2d\uff0c18 \u5c81\u7684\u5f20\u4e09\u8003\u8bd5\u5f97\u4e86 98 \u5206\uff0c\u5f88\u4e0d\u9519\u7684\u6210\u7ee9\uff0c\u6211\u4eec\u628a\u5f20\u4e09\u548c\u6210\u7ee9\u653e\u5230\u4e86 HashMap \u4e2d\uff0c\u7136\u540e\u51c6\u5907\u8f93\u51fa\u5f20\u4e09\u7684\u6210\u7ee9\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>null<\/code><\/pre>\n\n\n\n<p>\u5f88\u4e0d\u5de7\uff0c\u7ed3\u679c\u4e3a null\uff0c\u800c\u4e0d\u662f\u9884\u671f\u5f53\u4e2d\u7684 98\u3002\u8fd9\u662f\u4e3a\u4ec0\u4e48\u5462\uff1f<\/p>\n\n\n\n<p>\u539f\u56e0\u5c31\u5728\u4e8e\u91cd\u5199&nbsp;<code>equals()<\/code>&nbsp;\u65b9\u6cd5\u7684\u65f6\u5019\u6ca1\u6709\u91cd\u5199&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u3002\u9ed8\u8ba4\u60c5\u51b5\u4e0b\uff0c<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u662f\u4e00\u4e2a\u672c\u5730\u65b9\u6cd5\uff0c\u4f1a\u8fd4\u56de\u5bf9\u8c61\u7684\u5b58\u50a8\u5730\u5740\uff0c\u663e\u7136&nbsp;<code>put()<\/code>&nbsp;\u4e2d\u7684 s1 \u548c&nbsp;<code>get()<\/code>&nbsp;\u4e2d\u7684&nbsp;<code>new Student(18, \"\u5f20\u4e09\")<\/code>&nbsp;\u662f\u4e24\u4e2a\u5bf9\u8c61\uff0c\u5b83\u4eec\u7684\u5b58\u50a8\u5730\u5740\u80af\u5b9a\u662f\u4e0d\u540c\u7684\u3002<\/p>\n\n\n\n<p>HashMap \u7684&nbsp;<code>get()<\/code>&nbsp;\u65b9\u6cd5\u4f1a\u8c03\u7528&nbsp;<code>hash(key.hashCode())<\/code>&nbsp;\u8ba1\u7b97\u5bf9\u8c61\u7684\u54c8\u5e0c\u503c\uff0c\u867d\u7136\u4e24\u4e2a\u4e0d\u540c\u7684&nbsp;<code>hashCode()<\/code>&nbsp;\u7ed3\u679c\u7ecf\u8fc7&nbsp;<code>hash()<\/code>&nbsp;\u65b9\u6cd5\u8ba1\u7b97\u540e\u6709\u53ef\u80fd\u5f97\u5230\u76f8\u540c\u7684\u7ed3\u679c\uff0c\u4f46\u8fd9\u79cd\u6982\u7387\u5fae\u4e4e\u5176\u5fae\uff0c\u6240\u4ee5\u5c31\u5bfc\u81f4&nbsp;<code>scores.get(new Student(18, \"\u5f20\u4e09\"))<\/code>&nbsp;\u65e0\u6cd5\u5f97\u5230\u9884\u671f\u7684\u503c 18\u3002<\/p>\n\n\n\n<p>\u600e\u4e48\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\u5462\uff1f\u5f88\u7b80\u5355\uff0c\u91cd\u5199&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code> @Override\n public int hashCode() {\n     return Objects.hash(age, name);\n }<\/code><\/pre>\n\n\n\n<p><a href=\"https:\/\/javabetter.cn\/common-tool\/Objects.html\" target=\"_blank\" rel=\"noreferrer noopener\">Objects \u7c7b<\/a>\u7684&nbsp;<code>hash()<\/code>&nbsp;\u65b9\u6cd5\u53ef\u4ee5\u9488\u5bf9\u4e0d\u540c\u6570\u91cf\u7684\u53c2\u6570\u751f\u6210\u65b0\u7684&nbsp;<code>hashCode()<\/code>&nbsp;\u503c\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>public static int hashCode(Object a&#91;]) {\n if (a == null)\n     return 0;\n\n int result = 1;\n\n for (Object element : a)\n     result = 31 * result + (element == null ? 0 : element.hashCode());\n\n return result;\n}<\/code><\/pre>\n\n\n\n<p>\u4ee3\u7801\u4f3c\u4e4e\u5f88\u7b80\u5355\uff0c\u5f52\u7eb3\u51fa\u7684\u6570\u5b66\u516c\u5f0f\u5982\u4e0b\u6240\u793a\uff08n \u4e3a\u5b57\u7b26\u4e32\u957f\u5ea6\uff09\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" width=\"668\" height=\"46\" src=\"https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/image-26.png\" alt=\"\" class=\"wp-image-622\" srcset=\"https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/image-26.png 668w, https:\/\/www.ikaros.love\/wp-content\/uploads\/2024\/11\/image-26-300x21.png 300w\" sizes=\"(max-width: 668px) 100vw, 668px\" \/><\/figure>\n\n\n\n<p>\u6ce8\u610f\uff1a31 \u662f\u4e2a\u5947\u8d28\u6570\uff0c\u4e0d\u5927\u4e0d\u5c0f\uff0c\u4e00\u822c\u8d28\u6570\u90fd\u975e\u5e38\u9002\u5408\u54c8\u5e0c\u8ba1\u7b97\uff0c\u5076\u6570\u76f8\u5f53\u4e8e\u79fb\u4f4d\u8fd0\u7b97\uff0c\u5bb9\u6613\u6ea2\u51fa\uff0c\u9020\u6210\u6570\u636e\u4fe1\u606f\u4e22\u5931\u3002<\/p>\n\n\n\n<p>\u8fd9\u5c31\u610f\u5473\u7740\u5e74\u7eaa\u548c\u59d3\u540d\u76f8\u540c\u7684\u60c5\u51b5\u4e0b\uff0c\u4f1a\u5f97\u5230\u76f8\u540c\u7684\u54c8\u5e0c\u503c\u3002<code>scores.get(new Student(18, \"\u5f20\u4e09\"))<\/code>&nbsp;\u5c31\u4f1a\u8fd4\u56de 98 \u7684\u9884\u671f\u503c\u4e86\u3002<\/p>\n\n\n\n<p>\u300aJava \u7f16\u7a0b\u601d\u60f3\u300b\u8fd9\u672c\u5723\u7ecf\u4e2d\u6709\u4e00\u6bb5\u8bdd\uff0c\u5bf9&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u8fdb\u884c\u4e86\u4e00\u6bb5\u63cf\u8ff0\u3002<\/p>\n\n\n\n<blockquote class=\"wp-block-quote\">\n<p>\u8bbe\u8ba1&nbsp;<code>hashCode()<\/code>&nbsp;\u65f6\u6700\u91cd\u8981\u7684\u56e0\u7d20\u5c31\u662f\uff1a\u65e0\u8bba\u4f55\u65f6\uff0c\u5bf9\u540c\u4e00\u4e2a\u5bf9\u8c61\u8c03\u7528&nbsp;<code>hashCode()<\/code>&nbsp;\u90fd\u5e94\u8be5\u751f\u6210\u540c\u6837\u7684\u503c\u3002\u5982\u679c\u5728\u5c06\u4e00\u4e2a\u5bf9\u8c61\u7528&nbsp;<code>put()<\/code>&nbsp;\u65b9\u6cd5\u6dfb\u52a0\u8fdb HashMap \u65f6\u4ea7\u751f\u4e00\u4e2a&nbsp;<code>hashCode()<\/code>&nbsp;\u503c\uff0c\u800c\u7528&nbsp;<code>get()<\/code>&nbsp;\u65b9\u6cd5\u53d6\u51fa\u65f6\u5374\u4ea7\u751f\u4e86\u53e6\u5916\u4e00\u4e2a&nbsp;<code>hashCode()<\/code>&nbsp;\u503c\uff0c\u90a3\u4e48\u5c31\u65e0\u6cd5\u91cd\u65b0\u53d6\u5f97\u8be5\u5bf9\u8c61\u4e86\u3002\u6240\u4ee5\uff0c\u5982\u679c\u4f60\u7684&nbsp;<code>hashCode()<\/code>&nbsp;\u65b9\u6cd5\u4f9d\u8d56\u4e8e\u5bf9\u8c61\u4e2d\u6613\u53d8\u7684\u6570\u636e\uff0c\u7528\u6237\u5c31\u8981\u5f53\u5fc3\u4e86\uff0c\u56e0\u4e3a\u6b64\u6570\u636e\u53d1\u751f\u53d8\u5316\u65f6\uff0c<code>hashCode()<\/code>&nbsp;\u5c31\u4f1a\u751f\u6210\u4e00\u4e2a\u4e0d\u540c\u7684\u54c8\u5e0c\u503c\uff0c\u76f8\u5f53\u4e8e\u4ea7\u751f\u4e86\u4e00\u4e2a\u4e0d\u540c\u7684\u952e\u3002<\/p>\n<\/blockquote>\n\n\n\n<p>\u4e5f\u5c31\u662f\u8bf4\uff0c\u5982\u679c\u5728\u91cd\u5199&nbsp;<code>hashCode()<\/code>&nbsp;\u548c&nbsp;<code>equals()<\/code>&nbsp;\u65b9\u6cd5\u65f6\uff0c\u5bf9\u8c61\u4e2d\u67d0\u4e2a\u5b57\u6bb5\u5bb9\u6613\u53d1\u751f\u6539\u53d8\uff0c\u90a3\u4e48\u6700\u597d\u820d\u5f03\u8fd9\u4e9b\u5b57\u6bb5\uff0c\u4ee5\u514d\u4ea7\u751f\u4e0d\u53ef\u9884\u671f\u7684\u7ed3\u679c\u3002<\/p>\n\n\n\n<p>\u597d\u3002\u6709\u4e86\u4e0a\u9762\u8fd9\u4e9b\u5185\u5bb9\u4f5c\u4e3a\u57fa\u7840\u540e\uff0c\u6211\u4eec\u56de\u5934\u518d\u6765\u770b\u770b\u672c\u5730\u65b9\u6cd5&nbsp;<code>hashCode()<\/code>&nbsp;\u7684 C++ \u6e90\u7801\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>static inline intptr_t get_next_hash(Thread* current, oop obj) {\n  intptr_t value = 0;\n  if (hashCode == 0) {\n    \/\/ \u8fd9\u79cd\u5f62\u5f0f\u4f7f\u7528\u5168\u5c40\u7684 Park-Miller \u968f\u673a\u6570\u751f\u6210\u5668\u3002\n    \/\/ \u5728 MP \u7cfb\u7edf\u4e0a\uff0c\u6211\u4eec\u5c06\u5bf9\u5168\u5c40\u53d8\u91cf\u8fdb\u884c\u5927\u91cf\u7684\u8bfb\u5199\u8bbf\u95ee\uff0c\u56e0\u6b64\u8be5\u673a\u5236\u4f1a\u5f15\u53d1\u5927\u91cf\u7684\u4e00\u81f4\u6027\u901a\u4fe1\u3002\n    value = os::random();\n  } else if (hashCode == 1) {\n    \/\/ \u8fd9\u79cd\u53d8\u4f53\u5728 STW\uff08Stop The World\uff09\u64cd\u4f5c\u4e4b\u95f4\u5177\u6709\u7a33\u5b9a\uff08\u5e42\u7b49\uff09\u7684\u7279\u6027\u3002\n    \/\/ \u5728\u4e00\u4e9b 1-0 \u540c\u6b65\u65b9\u6848\u4e2d\uff0c\u8fd9\u53ef\u80fd\u5f88\u6709\u7528\u3002\n    intptr_t addr_bits = cast_from_oop&lt;intptr_t&gt;(obj) &gt;&gt; 3;\n    value = addr_bits ^ (addr_bits &gt;&gt; 5) ^ GVars.stw_random;\n  } else if (hashCode == 2) {\n    value = 1;            \/\/ \u7528\u4e8e\u654f\u611f\u6027\u6d4b\u8bd5\n  } else if (hashCode == 3) {\n    value = ++GVars.hc_sequence;\n  } else if (hashCode == 4) {\n    value = cast_from_oop&lt;intptr_t&gt;(obj);\n  } else {\n    \/\/ Marsaglia \u7684\u5f02\u6216\u79fb\u4f4d\u65b9\u6848\uff0c\u5177\u6709\u7ebf\u7a0b\u7279\u5b9a\u7684\u72b6\u6001\n    \/\/ \u8fd9\u53ef\u80fd\u662f\u6700\u597d\u7684\u6574\u4f53\u5b9e\u73b0 -- \u6211\u4eec\u53ef\u80fd\u4f1a\u5728\u672a\u6765\u7684\u7248\u672c\u4e2d\u5c06\u5176\u8bbe\u4e3a\u9ed8\u8ba4\u5b9e\u73b0\u3002\n    unsigned t = current-&gt;_hashStateX;\n    t ^= (t &lt;&lt; 11);\n    current-&gt;_hashStateX = current-&gt;_hashStateY;\n    current-&gt;_hashStateY = current-&gt;_hashStateZ;\n    current-&gt;_hashStateZ = current-&gt;_hashStateW;\n    unsigned v = current-&gt;_hashStateW;\n    v = (v ^ (v &gt;&gt; 19)) ^ (t ^ (t &gt;&gt; 8));\n    current-&gt;_hashStateW = v;\n    value = v;\n  }\n\n  value &amp;= markWord::hash_mask;\n  if (value == 0) value = 0xBAD;\n  assert(value != markWord::no_hash, \"invariant\");\n  return value;\n}<\/code><\/pre>\n\n\n\n<p>\u5982\u679c\u6ca1\u6709 C++ \u57fa\u7840\u7684\u8bdd\uff0c\u4e0d\u7528\u7ec6\u81f4\u53bb\u770b\u6bcf\u4e00\u884c\u4ee3\u7801\uff0c\u6211\u4eec\u53ea\u901a\u8fc7\u8868\u9762\u53bb\u4e86\u89e3\u4e00\u4e0b&nbsp;<code>get_next_hash()<\/code>&nbsp;\u8fd9\u4e2a\u65b9\u6cd5\u5c31\u884c\u3002\u5176\u4e2d\u7684&nbsp;<code>hashCode<\/code>&nbsp;\u53d8\u91cf\u662f JVM \u542f\u52a8\u65f6\u7684\u4e00\u4e2a\u5168\u5c40\u53c2\u6570\uff0c\u53ef\u4ee5\u901a\u8fc7\u5b83\u6765\u5207\u6362\u54c8\u5e0c\u503c\u7684\u751f\u6210\u7b56\u7565\u3002<\/p>\n\n\n\n<ul>\n<li><code>hashCode==0<\/code>\uff0c\u8c03\u7528\u64cd\u4f5c\u7cfb\u7edf OS \u7684&nbsp;<code>random()<\/code>&nbsp;\u65b9\u6cd5\u8fd4\u56de\u968f\u673a\u6570\u3002<\/li>\n\n\n\n<li><code>hashCode == 1<\/code>\uff0c\u5728 STW\uff08stop-the-world\uff09\u64cd\u4f5c\u4e2d\uff0c\u8fd9\u79cd\u7b56\u7565\u901a\u5e38\u7528\u4e8e\u540c\u6b65\u65b9\u6848\u4e2d\u3002\u5229\u7528\u5bf9\u8c61\u5730\u5740\u8fdb\u884c\u8ba1\u7b97\uff0c\u4f7f\u7528\u4e0d\u7ecf\u5e38\u66f4\u65b0\u7684\u968f\u673a\u6570\uff08<code>GVars.stw_random<\/code>\uff09\u53c2\u4e0e\u5176\u4e2d\u3002<\/li>\n\n\n\n<li><code>hashCode == 2<\/code>\uff0c\u4f7f\u7528\u8fd4\u56de 1\uff0c\u7528\u4e8e\u67d0\u4e9b\u60c5\u51b5\u4e0b\u7684\u6d4b\u8bd5\u3002<\/li>\n\n\n\n<li><code>hashCode == 3<\/code>\uff0c\u4ece 0 \u5f00\u59cb\u8ba1\u7b97\u54c8\u5e0c\u503c\uff0c\u4e0d\u662f\u7ebf\u7a0b\u5b89\u5168\u7684\uff0c\u591a\u4e2a\u7ebf\u7a0b\u53ef\u80fd\u4f1a\u5f97\u5230\u76f8\u540c\u7684\u54c8\u5e0c\u503c\u3002<\/li>\n\n\n\n<li><code>hashCode == 4<\/code>\uff0c\u4e0e\u521b\u5efa\u5bf9\u8c61\u7684\u5185\u5b58\u4f4d\u7f6e\u6709\u5173\uff0c\u539f\u6837\u8f93\u51fa\u3002<\/li>\n\n\n\n<li><code>hashCode == 5<\/code>\uff0c\u9ed8\u8ba4\u503c\uff0c\u652f\u6301\u591a\u7ebf\u7a0b\uff0c\u4f7f\u7528\u4e86 Marsaglia \u7684 xor-shift \u7b97\u6cd5\u4ea7\u751f\u4f2a\u968f\u673a\u6570\u3002\u6240\u8c13\u7684 xor-shift \u7b97\u6cd5\uff0c\u7b80\u5355\u6765\u8bf4\uff0c\u770b\u8d77\u6765\u5c31\u662f\u4e00\u4e2a\u79fb\u4f4d\u5bc4\u5b58\u5668\uff0c\u6bcf\u6b21\u79fb\u5165\u7684\u4f4d\u7531\u5bc4\u5b58\u5668\u4e2d\u82e5\u5e72\u4f4d\u53d6\u5f02\u6216\u751f\u6210\u3002\u6240\u8c13\u7684\u4f2a\u968f\u673a\u6570\uff0c\u4e0d\u662f\u5b8c\u5168\u968f\u673a\u7684\uff0c\u4f46\u662f\u771f\u968f\u673a\u751f\u6210\u6bd4\u8f83\u56f0\u96be\uff0c\u6240\u4ee5\u53ea\u8981\u80fd\u901a\u8fc7\u4e00\u5b9a\u7684\u968f\u673a\u6570\u7edf\u8ba1\u68c0\u6d4b\uff0c\u5c31\u53ef\u4ee5\u5f53\u4f5c\u771f\u968f\u673a\u6570\u6765\u4f7f\u7528\u3002<\/li>\n<\/ul>\n\n\n\n<p>\u8fd9\u91cc\u7b80\u5355\u603b\u7ed3\u4e0b\u3002<\/p>\n\n\n\n<p>\u5728 Java \u4e2d\uff0c<code>hashCode()<\/code>\u65b9\u6cd5\u662f\u5b9a\u4e49\u5728&nbsp;<code>java.lang.Object<\/code>&nbsp;\u7c7b\u4e2d\u7684\u4e00\u4e2a\u65b9\u6cd5\uff0c\u8be5\u7c7b\u662f\u6240\u6709 Java \u6240\u6709\u7c7b\u7684\u7236\u7c7b\u3002\u56e0\u6b64\uff0c\u6bcf\u4e2a Java \u5bf9\u8c61\u90fd\u53ef\u4ee5\u8c03\u7528&nbsp;<code>hashCode()<\/code>\u65b9\u6cd5\u3002<code>hashCode()<\/code>\u65b9\u6cd5\u4e3b\u8981\u7528\u4e8e\u652f\u6301\u54c8\u5e0c\u8868\uff08\u5982 java.util.HashMap\uff09\uff0c\u8fd9\u4e9b\u6570\u636e\u7ed3\u6784\u4f7f\u7528\u54c8\u5e0c\u7b97\u6cd5\u80fd\u5b9e\u73b0\u5feb\u901f\u67e5\u627e\u3001\u63d2\u5165\u548c\u5220\u9664\u64cd\u4f5c\u3002<\/p>\n\n\n\n<p><code>hashCode()<\/code>\u65b9\u6cd5\u7684\u4e3b\u8981\u76ee\u7684\u662f\u8fd4\u56de\u4e00\u4e2a\u6574\u6570\uff0c\u8fd9\u4e2a\u6574\u6570\u79f0\u4e3a\u54c8\u5e0c\u7801\uff0c\u5b83\u4ee3\u8868\u4e86\u5bf9\u8c61\u5728\u5185\u5b58\u4e2d\u7684\u4e00\u79cd\u8fd1\u4f3c\u8868\u793a\u3002\u54c8\u5e0c\u7801\u7528\u4e8e\u5c06\u5bf9\u8c61\u6620\u5c04\u5230\u54c8\u5e0c\u8868\u4e2d\u7684\u4e00\u4e2a\u7279\u5b9a\u7684\u4f4d\u7f6e\u3002\u4e24\u4e2a\u76f8\u7b49\u7684\u5bf9\u8c61\uff08\u6839\u636e&nbsp;<a href=\"https:\/\/javabetter.cn\/string\/equals.html\" target=\"_blank\" rel=\"noreferrer noopener\"><code>equals()<\/code>\u65b9\u6cd5\u6bd4\u8f83<\/a>\uff09\u5e94\u8be5\u5177\u6709\u76f8\u540c\u7684\u54c8\u5e0c\u7801\u3002\u7136\u800c\uff0c\u5177\u6709\u76f8\u540c\u54c8\u5e0c\u7801\u7684\u4e24\u4e2a\u5bf9\u8c61\u5e76\u4e0d\u4e00\u5b9a\u76f8\u7b49\u3002<\/p>\n\n\n\n<p>\u5f53\u4f60\u521b\u5efa\u4e00\u4e2a\u81ea\u5b9a\u4e49\u7c7b\u5e76\u8986\u76d6&nbsp;<code>equals()<\/code>\u65b9\u6cd5\u65f6\uff0c\u901a\u5e38\u4e5f\u9700\u8981\u8986\u76d6&nbsp;<code>hashCode()<\/code>\u65b9\u6cd5\uff0c\u4ee5\u786e\u4fdd\u76f8\u7b49\u7684\u5bf9\u8c61\u5177\u6709\u76f8\u540c\u7684\u54c8\u5e0c\u7801\u3002\u8fd9\u6709\u52a9\u4e8e\u63d0\u9ad8\u54c8\u5e0c\u8868\u5728\u4f7f\u7528\u81ea\u5b9a\u4e49\u7c7b\u7684\u5bf9\u8c61\u4f5c\u4e3a\u952e\u65f6\u7684\u51c6\u786e\u6027\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u642c\u8fd0\u81ea Java hashCod&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":620,"comment_status":"open","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[179,147],"_links":{"self":[{"href":"https:\/\/www.ikaros.love\/index.php?rest_route=\/wp\/v2\/posts\/619"}],"collection":[{"href":"https:\/\/www.ikaros.love\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ikaros.love\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ikaros.love\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ikaros.love\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=619"}],"version-history":[{"count":1,"href":"https:\/\/www.ikaros.love\/index.php?rest_route=\/wp\/v2\/posts\/619\/revisions"}],"predecessor-version":[{"id":623,"href":"https:\/\/www.ikaros.love\/index.php?rest_route=\/wp\/v2\/posts\/619\/revisions\/623"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.ikaros.love\/index.php?rest_route=\/wp\/v2\/media\/620"}],"wp:attachment":[{"href":"https:\/\/www.ikaros.love\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=619"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ikaros.love\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=619"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ikaros.love\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=619"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}