{"id":1372,"date":"2019-02-12T20:30:57","date_gmt":"2019-02-12T11:30:57","guid":{"rendered":"https:\/\/www.bold.ne.jp\/engineer-club\/?p=1372"},"modified":"2025-10-06T17:01:22","modified_gmt":"2025-10-06T08:01:22","slug":"java-hashcode","status":"publish","type":"post","link":"https:\/\/www.bold.ne.jp\/engineer-club\/java-hashcode","title":{"rendered":"Java\u3092\u9670\u304b\u3089\u652f\u3048\u308bhashCode\u3068\u306f\uff1fhashCode\u306e\u4ed5\u7d44\u307f\u3068\u5b9f\u88c5\u65b9\u6cd5"},"content":{"rendered":"<p><strong>Object.hashCode\u306f\u3001\u547c\u3073\u51fa\u3055\u308c\u305f\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u306e\u7279\u5fb4\u3092\u8868\u3059\u300c\u30cf\u30c3\u30b7\u30e5\u5024\u300d\u3092\u8fd4\u3059\u30e1\u30bd\u30c3\u30c9\u3067\u3059\u3002<\/strong><\/p>\n<p>\u3053\u306e\u30cf\u30c3\u30b7\u30e5\u5024\u306f<span>HashMap<\/span>\u3084<span>HashSet<\/span>\u306a\u3069\u306e<span>Java<\/span>\u6a19\u6e96<span>API<\/span>\u306b\u3042\u308b\u30af\u30e9\u30b9\u306e\u591a\u304f\u3067\u4f7f\u308f\u308c\u307e\u3059\u3002<br \/>\n\u305d\u3057\u3066\u3001<span>hashCode<\/span>\u306f<span>Object.equals<\/span>\u3068\u5b9f\u306b\u6df1\u3044\u95a2\u4fc2\u304c\u3042\u308b\u3082\u306e\u306a\u306e\u3067\u3059\u3002<\/p>\n<p>\u3067\u3059\u304b\u3089\u3001<span>hashCode<\/span>\u3068<span>equals<\/span>\u304c\u3057\u3063\u304b\u308a\u5b9f\u88c5\u3055\u308c\u3066\u3044\u306a\u3044\u3068\u3001\u305d\u308c\u3089\u306e\u30af\u30e9\u30b9\u304c\u52d5\u3044\u3066\u307b\u3057\u3044\u3088\u3046\u306b\u52d5\u3044\u3066\u304f\u308c\u307e\u305b\u3093\u3002<br \/>\n<span>hashCode<\/span>\u3068<span>equals<\/span>\u306f\u4e00\u5fc3\u540c\u4f53\u3068\u3082\u3044\u3048\u308b\u30e1\u30bd\u30c3\u30c9\u306a\u306e\u3067\u3059\u3002<\/p>\n<p>\u3053\u306e\u8a18\u4e8b\u3067\u306f\u3001\u305d\u3093\u306a\u5927\u4e8b\u306a\u30e1\u30bd\u30c3\u30c9<span>hashCode<\/span>\u306b\u3064\u3044\u3066\u3001\u8003\u3048\u65b9\u3068\u5b9f\u4f8b\u3092\u4ea4\u3048\u306a\u304c\u3089\u3001\u521d\u5fc3\u8005\u5411\u3051\u306b\u304a\u4f1d\u3048\u3057\u307e\u3059\u3002<\/p>\n<p>\u203b\u3053\u306e\u8a18\u4e8b\u306e\u30b5\u30f3\u30d7\u30eb\u306f\u3001<span>Java 11<\/span>\u306e\u74b0\u5883\u3067\u52d5\u4f5c\u78ba\u8a8d\u3057\u3066\u3044\u307e\u3059<\/p>\n<div id=\"toc_container\" class=\"no_bullets\"><p class=\"toc_title\">\u76ee\u6b21<\/p><ul class=\"toc_list\"><li><a href=\"#JavahashCode\">\uff11\uff0e\u3010Java\u3011hashCode\u306f\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u306e\u7279\u5fb4\u3092\u8868\u3059\u6570\u5b57\u3092\u5f97\u308b\u3082\u306e<\/a><\/li><li><a href=\"#hashCode\">\uff12\uff0ehashCode\u306f\u4e3b\u306b\u30cf\u30c3\u30b7\u30e5\u30c6\u30fc\u30d6\u30eb\u3067\u6d3b\u7528\u3059\u308b<\/a><\/li><li><a href=\"#hashCode-2\">\uff13\uff0ehashCode\u306f\u3057\u3063\u304b\u308a\u3068\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3059\u308b<\/a><ul><li><a href=\"#-hashCode\">\uff13-\uff11\uff0ehashCode\u3092\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3057\u306a\u3044\u3068\u99c4\u76ee\u306a\u4f8b<\/a><\/li><\/ul><\/li><li><a href=\"#equalshashCode3\">\uff14\uff0eequals\u3068hashCode\u3092\u7d50\u3073\u3064\u3051\u308b3\u3064\u306e\u30eb\u30fc\u30eb<\/a><\/li><li><a href=\"#hashCode-3\">\uff15\uff0ehashCode\u306e\u5177\u4f53\u7684\u306a\u8a08\u7b97\u65b9\u6cd5<\/a><ul><li><a href=\"#-JavaAPI\">\uff15-\uff11\uff0eJava\u306e\u6a19\u6e96API\u3092\u4f7f\u3046\u65b9\u6cd5<\/a><\/li><li><a href=\"#-Effective_JavahashCode\">\uff15-\uff12\uff0e\u3010\u53c2\u8003\u3011Effective Java\u3067\u306ehashCode\u8a08\u7b97\u65b9\u6cd5<\/a><\/li><\/ul><\/li><li><a href=\"#hashCode-4\">\uff16\uff0e\u3010\u767a\u5c55\u3011hashCode\u306e\u3042\u308c\u3053\u308c<\/a><ul><li><a href=\"#-hashCode-2\">\uff16-\uff11\uff0ehashCode\u306f\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3059\u308b\u3082\u306e<\/a><\/li><li><a href=\"#-hashCode-3\">\uff16-\uff12\uff0ehashCode\u3092\u81ea\u52d5\u751f\u6210\u3057\u3066\u697d\u3092\u3059\u308b<\/a><\/li><\/ul><\/li><li><a href=\"#i\">\uff17\uff0e\u3055\u3044\u3054\u306b<\/a><\/li><\/ul><\/div>\n<h2><span id=\"JavahashCode\">\uff11\uff0e\u3010Java\u3011hashCode\u306f\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u306e\u7279\u5fb4\u3092\u8868\u3059\u6570\u5b57\u3092\u5f97\u308b\u3082\u306e<\/span><\/h2>\n<p>\u7686\u3055\u3093\u306f\u3001<span>MD5<\/span>\u3084<span>SHA-2<\/span>\u306e\u3088\u3046\u306a\u30cf\u30c3\u30b7\u30e5\u95a2\u6570\u3068\u8a00\u3046\u3082\u306e\u3092\u3054\u5b58\u3058\u3067\u3057\u3087\u3046\u304b\u3002<\/p>\n<p>\u7c21\u5358\u306b\u8a00\u3048\u3070\u3001\u4f55\u304b\u306e\u30e2\u30ce\u304b\u3089\u4e00\u3064\u306e\u6570\u5b57\u3092\u4f5c\u308a\u51fa\u3059\u30a2\u30eb\u30b4\u30ea\u30ba\u30e0\u306e\u3053\u3068\u3067\u3059\u3002<br \/>\n\u540c\u3058\u30e2\u30ce\u306a\u3089\u3044\u3064\u3067\u3082\u3069\u3053\u3067\u3082\u540c\u3058\u6570\u5b57\u306b\u306a\u308a\u307e\u3059\u3057\u3001\u9055\u3046\u30e2\u30ce\u540c\u58eb\u306f\u540c\u3058\u6570\u5b57\u306b\u306a\u308b\u3079\u304f\u306a\u3089\u306a\u3044\u3088\u3046\u306b\u4ed5\u69d8\u304c\u8a2d\u8a08\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n<blockquote>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u3010\u53c2\u8003\u3011<\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <a href=\"https:\/\/ja.wikipedia.org\/wiki\/\u30cf\u30c3\u30b7\u30e5\u95a2\u6570\">https:\/\/ja.wikipedia.org\/wiki\/\u30cf\u30c3\u30b7\u30e5\u95a2\u6570<\/a><\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u2192\u30cf\u30c3\u30b7\u30e5\u95a2\u6570\u3068\u306f\u4f55\u304b\u3001\u304c\u8aac\u660e\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n<\/blockquote>\n<p>Java\u3067\u3082\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u306e\u30cf\u30c3\u30b7\u30e5\u95a2\u6570\u3068\u547c\u3079\u308b\u3082\u306e\u304c\u3042\u308a\u307e\u3059\u3002\u305d\u308c\u304c<span>int<\/span>\u3092\u623b\u3059<span>Object.hashCode<\/span>\u3067\u3059\u3002\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u306e<span>hashCode<\/span>\u3092\u547c\u3073\u51fa\u3059\u3068\u3001\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u81ea\u8eab\u306e\u7279\u5fb4\u304c\u53cd\u6620\u3055\u308c\u305f<span>int<\/span>\u306e\u6570\u5b57\u3001\u3059\u306a\u308f\u3061\u30cf\u30c3\u30b7\u30e5\u5024\u304c\u623b\u3063\u3066\u304d\u307e\u3059\u3002<\/p>\n<pre class=\"prettyprint lang:default decode:true\">public int hashCode()\r\n\u623b\u308a\u5024:\r\n\t\u3053\u306e\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306e\u30cf\u30c3\u30b7\u30e5\u30fb\u30b3\u30fc\u30c9\u5024\u3002<\/pre>\n<p>hashCode\u306f<span>equals<\/span>\u3068\u540c\u3058\u304f\u3001\u3059\u3079\u3066\u306e\u30af\u30e9\u30b9\u306e\u30b9\u30fc\u30d1\u30fc\u30af\u30e9\u30b9\u3067\u3042\u308b<span>Object<\/span>\u306e\u30e1\u30bd\u30c3\u30c9\u306a\u306e\u3067\u3001\u3059\u3079\u3066\u306e\u30af\u30e9\u30b9\u3067\u4f7f\u3048\u307e\u3059\u3002\u3053\u308c\u3092<span>Java<\/span>\u306e\u5185\u90e8\u3067\u306f\u8272\u3005\u3068\u6d3b\u7528\u3057\u3066\u3044\u308b\u306e\u3067\u3059\u3002<\/p>\n<pre class=\"prettyprint lang:default decode:true\">String str1 = \"\u3042\u3044\u3046\u3048\u304a\";\r\nString str2 = \"\u3042\u3044\u3046\u3048\u304aA\"; \/\/ \u4e2d\u8eab\u304c\u3061\u3087\u3063\u3068\u9055\u3046\u3060\u3051\u3067\u3082\u2026\r\nint hashCode1 = str1.hashCode();\r\nint hashCode2 = str2.hashCode();\r\nSystem.out.println(hashCode1); \/\/ \u2192 -1095354298\r\nSystem.out.println(hashCode2); \/\/ \u2192 403755195\u3001\u5168\u7136\u9055\u3046\u6570\u5b57\u306b\u306a\u308b!!<\/pre>\n<h2><span id=\"hashCode\">\uff12\uff0ehashCode\u306f\u4e3b\u306b\u30cf\u30c3\u30b7\u30e5\u30c6\u30fc\u30d6\u30eb\u3067\u6d3b\u7528\u3059\u308b<\/span><\/h2>\n<p>hashCode\u3067\u5f97\u3089\u308c\u308b\u6570\u5b57\u306f\u3001\u300c\u30cf\u30c3\u30b7\u30e5\u30c6\u30fc\u30d6\u30eb\u300d\u3068\u3044\u3046\u30c7\u30fc\u30bf\u69cb\u9020\u3067\u4e3b\u306b\u4f7f\u308f\u308c\u307e\u3059\u3002\u30cf\u30c3\u30b7\u30e5\u30c6\u30fc\u30d6\u30eb\u306e\u4e2d\u3067\u30c7\u30fc\u30bf\u3092\u52b9\u7387\u7684\u306b\u5206\u985e\u3057\u3064\u3064\u3001\u30c7\u30fc\u30bf\u3092\u9ad8\u901f\u306b\u691c\u7d22\u3059\u308b\u305f\u3081\u306e\u30ad\u30fc\u60c5\u5831\u3068\u3057\u3066\u3001<span>hashCode<\/span>\u3067\u5f97\u3089\u308c\u308b\u6570\u5b57\u3092\u4f7f\u3046\u306e\u3067\u3059\u3002\u30cf\u30c3\u30b7\u30e5\u30c6\u30fc\u30d6\u30eb\u4ee5\u5916\u3067\u306f\u3001\u4f8b\u3048\u3070\u30c7\u30fc\u30bf\u306e\u30ad\u30e3\u30c3\u30b7\u30e5\u306a\u3069\u3067\u3082\u6d3b\u7528\u3055\u308c\u307e\u3059\u3002<\/p>\n<blockquote>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u3010\u53c2\u8003\u3011<\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <a href=\"https:\/\/ja.wikipedia.org\/wiki\/\u30cf\u30c3\u30b7\u30e5\u30c6\u30fc\u30d6\u30eb\">https:\/\/ja.wikipedia.org\/wiki\/\u30cf\u30c3\u30b7\u30e5\u30c6\u30fc\u30d6\u30eb<\/a><\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u2192\u30cf\u30c3\u30b7\u30e5\u30c6\u30fc\u30d6\u30eb\u3068\u306f\u4f55\u304b\u3001\u304c\u8aac\u660e\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n<\/blockquote>\n<p>\u30cf\u30c3\u30b7\u30e5\u30c6\u30fc\u30d6\u30eb\u306f\u3001<span>Java<\/span>\u3067\u306f<span>HashMap<\/span>\u3084<span>HashSet<\/span>\u306e\u5185\u90e8\u3067\u4f7f\u308f\u308c\u3066\u3044\u307e\u3059\u3002\u3067\u3059\u304b\u3089\u3001<span>HashMap<\/span>\u306e\u30ad\u30fc\u3001<span>HashSet<\/span>\u306e\u5024\u306b\u4f7f\u3046\u30af\u30e9\u30b9\u3067<span>hashCode<\/span>\u304c\u9069\u5207\u306b\u4f5c\u3089\u308c\u3066\u3044\u306a\u3051\u308c\u3070\u3001\u3053\u308c\u3089\u306e\u30cf\u30c3\u30b7\u30e5\u30c6\u30fc\u30d6\u30eb\u3092\u4f7f\u3046\u30af\u30e9\u30b9\u304c\u4e88\u60f3\u3069\u304a\u308a\u306b\u52d5\u3044\u3066\u304f\u308c\u306a\u3044\u306e\u3067\u3059\u3002<\/p>\n<h2><span id=\"hashCode-2\">\uff13\uff0ehashCode\u306f\u3057\u3063\u304b\u308a\u3068\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3059\u308b<\/span><\/h2>\n<p>hashCode\u304c\u304d\u3061\u3093\u3068\u4f5c\u3089\u308c\u3066\u3044\u308b\u304b\u3044\u306a\u3044\u304b\u3067\u3001\u5927\u304d\u304f\u9055\u3044\u304c\u51fa\u3066\u304d\u307e\u3059\u3002<\/p>\n<p>hashCode\u306f\u62bd\u8c61\u30e1\u30bd\u30c3\u30c9\u3067\u306f\u306a\u3044\u306e\u3067\u3001<span>Object<\/span>\u3067\u306e\u30c7\u30d5\u30a9\u30eb\u30c8\u5b9f\u88c5\u306f\u4e00\u5fdc\u3042\u308a\u307e\u3059\u304c\u3001\u305d\u308c\u305e\u308c\u306e\u30af\u30e9\u30b9\u306e\u3053\u3068\u3092\u8003\u3048\u3066\u304f\u308c\u305f\u30cf\u30c3\u30b7\u30e5\u5024\u3092\u623b\u3057\u3066\u306f\u304f\u308c\u306a\u3044\u306e\u3067\u3059\u3002<\/p>\n<pre class=\"prettyprint lang:default decode:true\">\/\/ Java 11\u306eObject\u306e\u30bd\u30fc\u30b9\u30b3\u30fc\u30c9\u304b\u3089\u629c\u7c8b\u3001native\u30e1\u30bd\u30c3\u30c9\u3092\u547c\u3073\u51fa\u3057\u3066\u3044\u308b\u3060\u3051\r\n    public native int hashCode();<\/pre>\n<h3><span id=\"-hashCode\">\uff13-\uff11\uff0ehashCode\u3092\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3057\u306a\u3044\u3068\u99c4\u76ee\u306a\u4f8b<\/span><\/h3>\n<p>\u4f8b\u3048\u3070\u3001<span>hashCode<\/span>\u3092\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3057\u306a\u3044\u3068\u4ee5\u4e0b\u306e\u3088\u3046\u306a\u52d5\u304d\u306e\u9055\u3044\u304c\u51fa\u3066\u304d\u307e\u3059\u3002<\/p>\n<p>\u3082\u3061\u308d\u3093\u5f8c\u8005\u304c\u610f\u56f3\u3069\u304a\u308a\u306e\u52d5\u304d\u306a\u306e\u3067\u3059\u304c\u3001<span>hashCode<\/span>\u3092\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3057\u3066\u3044\u308b\u304b\u3044\u306a\u3044\u304b\u3060\u3051\u3067\u3001\u51e6\u7406\u7d50\u679c\u304c\u5168\u7136\u9055\u3063\u3066\u304d\u3066\u3057\u307e\u3046\u306e\u3067\u3059\u3002<\/p>\n<pre class=\"prettyprint lang:default decode:true\">import java.util.HashMap;\r\n\r\nclass HashCodeSample1 {\r\n\tint id;\r\n\r\n\tHashCodeSample1(int id) {\r\n\t\tthis.id = id;\r\n\t}\r\n\r\n\tpublic boolean equals(Object obj) {\r\n\t\treturn id == ((HashCodeSample1) obj).id;\r\n\t}\r\n\r\n\t\/\/ \u3053\u306e\u30af\u30e9\u30b9\u3067\u306fhashCode\u3092\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3057\u3066\u3044\u306a\u3044\r\n\r\n\tpublic static void main(String[] args) {\r\n\t\tHashCodeSample1 sample1 = new HashCodeSample1(1);\r\n\t\tHashCodeSample1 sample2 = new HashCodeSample1(1);\r\n\r\n\t\tSystem.out.println(sample1.equals(sample2)); \/\/ \u2192 true\u3001sample1\u3068sample2\u306f\u610f\u5473\u7684\u306b\u306f\u540c\u3058\r\n\t\tSystem.out.println(sample1.hashCode()); \/\/ hashCode\u306f\u3001sample1\u3068sample2\u3067\u306f\u9055\u3046\u5024\r\n\t\tSystem.out.println(sample2.hashCode());\r\n\r\n\t\tHashMap&lt;HashCodeSample1, String&gt; hashMap = new HashMap&lt;&gt;(); \/\/ HashMap\u3092\u4f5c\u3063\u3066\u2026\r\n\t\thashMap.put(sample1, \"\u732b\"); \/\/ sample1\u3092\u30ad\u30fc\u306b\u5024\u3092\u8a2d\u5b9a\u3057\u3066\u2026\r\n\t\tString value = hashMap.get(sample2); \/\/ \u610f\u5473\u7684\u306b\u540c\u3058sample2\u3067\u5024\u3092\u53d6\u308a\u51fa\u3059\u3068\u2026\r\n\t\tSystem.out.println(value); \/\/ \u2192 null\u3001\u5024\u3067\u3042\u308b\"\u732b\"\u304c\u53d6\u308a\u51fa\u305b\u306a\u3044!!\r\n\t}\r\n}<\/pre>\n<pre class=\"prettyprint lang:default decode:true\">import java.util.HashMap;\r\n\r\nclass HashCodeSample2 {\r\n\tint id;\r\n\r\n\tHashCodeSample2(int id) {\r\n\t\tthis.id = id;\r\n\t}\r\n\r\n\tpublic boolean equals(Object obj) {\r\n\t\treturn id == ((HashCodeSample2) obj).id;\r\n\t}\r\n\r\n\t\/\/ Object.hashCode\u3092\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3057\u305f\u3002\u3054\u304f\u5358\u7d14\u306b\u81ea\u5206\u81ea\u8eab\u306eint\u3092\u623b\u3059\u3002\r\n\tpublic int hashCode() {\r\n\t\treturn id;\r\n\t}\r\n\r\n\tpublic static void main(String[] args) {\r\n\t\tHashCodeSample2 sample1 = new HashCodeSample2(1);\r\n\t\tHashCodeSample2 sample2 = new HashCodeSample2(1);\r\n\r\n\t\tSystem.out.println(sample1.equals(sample2)); \/\/ \u2192 true\u3001sample1\u3068sample2\u306f\u610f\u5473\u7684\u306b\u306f\u540c\u3058\r\n\t\tSystem.out.println(sample1.hashCode()); \/\/ hashCode\u306e\u7d50\u679c\u3082\u540c\u3058\u306b\u306a\u308b(id\u3092\u623b\u3057\u3066\u3044\u308b\u306e\u3067)\r\n\t\tSystem.out.println(sample2.hashCode());\r\n\r\n\t\tHashMap&lt;HashCodeSample2, String&gt; hashMap = new HashMap&lt;&gt;(); \/\/ HashMap\u3092\u4f5c\u3063\u3066\u2026\r\n\t\thashMap.put(sample1, \"\u732b\"); \/\/ sample1\u3092\u30ad\u30fc\u306b\u5024\u3092\u8a2d\u5b9a\u3057\u3066\u2026\r\n\t\tString value = hashMap.get(sample2); \/\/ \u610f\u5473\u7684\u306b\u540c\u3058sample2\u3067\u5024\u3092\u53d6\u308a\u51fa\u3059\u3068\u2026\r\n\t\tSystem.out.println(value); \/\/ \u2192 \"\u732b\"\u3001\u5024\u304c\u3061\u3083\u3093\u3068\u53d6\u308a\u51fa\u305b\u305f!!\r\n\t}\r\n}<\/pre>\n<h2><span id=\"equalshashCode3\">\uff14\uff0eequals\u3068<span>hashCode<\/span>\u3092\u7d50\u3073\u3064\u3051\u308b<span>3<\/span>\u3064\u306e\u30eb\u30fc\u30eb<\/span><\/h2>\n<p>equals\u3068<span>hashCode<\/span>\u306f\u304a\u4e92\u3044\u306b\u6df1\u304f\u95a2\u4fc2\u3057\u3066\u3044\u307e\u3059\u3002\u4e21\u65b9\u3068\u3082\u300c\u540c\u3058\u300d\u304b\u8abf\u3079\u308b\u3082\u306e\u3067\u3059\u304c\u3001\u7528\u9014\u304c\u9055\u3044\u307e\u3059\u3002\u3067\u3082\u3001\u304d\u3061\u3093\u3068\u9023\u643a\u3057\u3066\u3044\u306a\u3051\u308c\u3070\u306a\u308a\u307e\u305b\u3093\u3002<\/p>\n<p>\u4ee5\u4e0b\u306e<span>3<\/span>\u3064\u306e\u30eb\u30fc\u30eb\u306e\u4e2d\u3067\u3001\u91cd\u8981\u306a\u306e\u306f<span>1<\/span>\u3068<span>2<\/span>\u3067\u3059\u3002<span>hashCode<\/span>\u306f\u3053\u308c\u3092\u5b88\u308b\u3088\u3046\u306b\u4f5c\u3089\u306a\u3051\u308c\u3070\u306a\u308a\u307e\u305b\u3093\u3002<span>equals<\/span>\u306e\u52d5\u304d\u3092\u3092\u5909\u3048\u305f\u306a\u3089\u3001<span>hashCode<\/span>\u3082\u5fc5\u305a\u30bb\u30c3\u30c8\u3067\u5909\u3048\u307e\u3057\u3087\u3046\u3001\u3068\u3044\u3046\u3053\u3068\u3067\u3082\u3042\u308a\u307e\u3059\u3002<\/p>\n<ol>\n<li>equals\u3067\u306e\u5224\u65ad\u3067\u4f7f\u3046\u30d5\u30a3\u30fc\u30eb\u30c9\u304c\u5909\u308f\u3089\u306a\u3044\u306a\u3089\u3001<span>hashCode<\/span>\u306e\u5024\u3082\u5909\u308f\u3089\u306a\u3044<\/li>\n<li>equals\u306e\u7d50\u679c\u304c<span>true<\/span>\u306a\u3089\u3001\u9055\u3046\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u3067\u3082<span>hashCode<\/span>\u306e\u5024\u306f\u540c\u3058\u306b\u306a\u308b<\/li>\n<li>equals\u306e\u7d50\u679c\u304c<span>false<\/span>\u306a\u3089\u3001<span>hashCode<\/span>\u306e\u5024\u306f\u9055\u308f\u306a\u304f\u3066\u3082\u3044\u3044<\/li>\n<\/ol>\n<p>hashCode\u306e\u5024\u306f\u81ea\u5206\u81ea\u8eab\u3092\u7279\u5fb4\u3065\u3051\u308b\u6570\u5b57\u3067\u3057\u304b\u306a\u304f\u3001\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u540c\u58eb\u306e\u7c21\u6613\u7684\u306a\u5206\u985e\u30fb\u8b58\u5225\u304c\u4e3b\u76ee\u7684\u3067\u3059\u3002<\/p>\n<p>int\u306f\u5168\u4f53\u3067<span>43<\/span>\u5104\u3068\u304a\u308a\u300c\u3057\u304b\u300d\u8868\u73fe\u3067\u304d\u306a\u3044<span>32bit<\/span>\u306e\u6570\u5b57\u306a\u306e\u3067\u3001\u9055\u3046\u30af\u30e9\u30b9\u306e\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u304c\u540c\u3058<span>int<\/span>\u3092\u623b\u3059\u3053\u3068\u3082\u3042\u308a\u3048\u307e\u3059\u3002\u3053\u308c\u3092\u8003\u616e\u306b\u5165\u308c\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<p>\u306a\u304a\u3001<span>equals<\/span>\u306b\u3064\u3044\u3066\u306f\u4ee5\u4e0b\u306e\u8a18\u4e8b\u3082\u53c2\u7167\u3057\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n\n<span style=\"text-decoration:none !important; background-color:#a61e58; color:white; padding:4px 13px; font-size:12px; font-weight:bold; position:relative; top:10px; z-index:1; left:11px;\">\u95a2\u9023\u8a18\u4e8b<\/span>\n<div class=\"blog-card\"><a target=\"_blank\" href=\"https:\/\/www.bold.ne.jp\/engineer-club\/java-equals\" style=\"text-decoration:none;\">\n    <div class=\"blog-card-thumbnail\"><img src='https:\/\/www.bold.ne.jp\/engineer-club\/wp-content\/uploads\/2018\/10\/shutterstock_568617811-600x366.jpg' alt='java equals\u3068\u306f\uff1fjava equals\u3092\u901a\u3058\u3066\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u304c\u300c\u540c\u3058\u300d\u304b\u30c1\u30a7\u30c3\u30af\u3057\u3088\u3046' width=160 height=98 \/><\/div>\n    <div class=\"blog-card-content\">\n        <div class=\"blog-card-title\">java equals\u3068\u306f\uff1fjava equals\u3092\u901a\u3058\u3066\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u304c\u300c\u540c\u3058\u300d\u304b\u30c1\u30a7\u30c3\u30af\u3057\u3088\u3046 <\/div>\n        <span style=\"font-size: 12px; font-weight: normal; position:relative; color:#666;\"><i class=\"fa fa-clock-o\"><\/i>&nbsp;2025\/10\/06<\/span>\n    <\/div>\n<div class=\"clear\"><\/div>\n<\/a><\/div>\n<h2><span id=\"hashCode-3\">\uff15\uff0ehashCode\u306e\u5177\u4f53\u7684\u306a\u8a08\u7b97\u65b9\u6cd5<\/span><\/h2>\n<p>\u57fa\u672c\u7684\u306b\u306f\u3001<span>equals<\/span>\u3067\u540c\u3058\u304b\u306e\u5224\u65ad\u306b\u4f7f\u3046\u30d5\u30a3\u30fc\u30eb\u30c9\u306e<span>hashCode<\/span>\u3092\u5bc4\u305b\u96c6\u3081\u305f\u3082\u306e\u3092\u3001<span>hashCode<\/span>\u304c\u623b\u3059\u6570\u5b57\u3068\u3057\u307e\u3059\u3002\u3053\u3046\u3059\u308b\u3068\u3001\u306a\u304b\u306a\u304b\u3044\u3044\u611f\u3058\u306b\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u3054\u3068\u306b\u30cf\u30c3\u30b7\u30e5\u5024\u304c\u7570\u306a\u308b\u304b\u3089\u3067\u3059\u3002<\/p>\n<p>hashCode\u306e\u8a08\u7b97\u65b9\u6cd5\u306b\u306f\u300c\u3053\u308c\u4e00\u629e<span>!!<\/span>\u300d\u3068\u8a00\u3046\u3082\u306e\u306f\u3042\u308a\u307e\u305b\u3093\u3002\u3067\u3082\u3001<span>Java<\/span>\u306e\u6a19\u6e96<span>API<\/span>\u306b\u306f\u30cf\u30c3\u30b7\u30e5\u30b3\u30fc\u30c9\u3092\u8a08\u7b97\u3059\u308b\u30e6\u30fc\u30c6\u30a3\u30ea\u30c6\u30a3\u30e1\u30bd\u30c3\u30c9\u304c\u3042\u308b\u306e\u3067\u3001\u305d\u308c\u3092\u4f7f\u3046\u3068\u30d7\u30ed\u30b0\u30e9\u30e0\u4e2d\u3067\u7d71\u4e00\u3057\u305f\u3084\u308a\u65b9\u3067\u8a08\u7b97\u3067\u304d\u307e\u3059\u3002<\/p>\n<p>\u57fa\u672c\u7684\u306b\u306f\u3001<span>equals<\/span>\u3067\u306e\u5224\u5b9a\u306b\u4f7f\u3046\u30d5\u30a3\u30fc\u30eb\u30c9\u5168\u3066\u306b\u5bfe\u3057\u3066\u500b\u5225\u306b\u30cf\u30c3\u30b7\u30e5\u5024\u3092\u8a08\u7b97\u3057\u3001\u5168\u3066\u3092\u8a08\u7b97\u7d50\u679c\u306b\u6df7\u305c\u8fbc\u3093\u3067\u6700\u7d42\u7684\u306a\u5024\u3092\u4f5c\u308a\u307e\u3059\u3002<\/p>\n<h3><span id=\"-JavaAPI\">\uff15-\uff11\uff0eJava\u306e\u6a19\u6e96<span>API<\/span>\u3092\u4f7f\u3046\u65b9\u6cd5<\/span><\/h3>\n<h4>\uff15-\uff11-\uff11\uff0e\u57fa\u672c\u7684\u306a\u5b9f\u88c5\u65b9\u6cd5<\/h4>\n<p>equals\u3067\u4f7f\u3046\u30d5\u30a3\u30fc\u30eb\u30c9\u5168\u3066\u306b\u5bfe\u3057\u3066\u3001\u4ee5\u4e0b\u306e\u3088\u3046\u306a\u611f\u3058\u3067\u8a08\u7b97\u3057\u307e\u3059\u3002\u8a08\u7b97\u5f0f\u3068<span>31<\/span>\u306f\u304a\u307e\u3058\u306a\u3044\u306e\u3088\u3046\u306a\u3082\u306e\u3060\u3068\u3001\u4eca\u306e\u3068\u3053\u308d\u306f\u3068\u308a\u3042\u3048\u305a\u8003\u3048\u3066\u304a\u3044\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n<pre class=\"prettyprint lang:default decode:true\">public int hashCode() {\r\n\tint result = 0\u3067\u306f\u306a\u3044\u4f55\u304b\u306e\u521d\u671f\u5024;\r\n\r\n\tresult = 31 * result + \u30d5\u30a3\u30fc\u30eb\u30c9\u3054\u3068\u306e\u30cf\u30c3\u30b7\u30e5\u5024;\r\n\t\/\/ \u2191\u3092equals\u3067\u4f7f\u3063\u3066\u3044\u308b\u30d5\u30a3\u30fc\u30eb\u30c9\u3059\u3079\u3066\u306b\u5bfe\u3057\u3066\u884c\u3046\r\n\r\n\treturn result;\r\n}<\/pre>\n<h4>\uff15-\uff11-\uff12\uff0e\u30d7\u30ea\u30df\u30c6\u30a3\u30d6\u578b\u306e\u30cf\u30c3\u30b7\u30e5\u5024\u306e\u8a08\u7b97\u65b9\u6cd5<\/h4>\n<p>\u30d7\u30ea\u30df\u30c6\u30a3\u30d6\u578b\u306e\u30e9\u30c3\u30d1\u30fc\u30af\u30e9\u30b9<span>(Integer<\/span>\u3001<span>Double<\/span>\u306a\u3069<span>)<\/span>\u306b\u3042\u308b<span>hashCode<\/span>\u3092\u4f7f\u3046\u3068\u3044\u3044\u3067\u3057\u3087\u3046\u3002<\/p>\n<p>\u5f15\u6570\u304c\u3042\u308b<span>hashCode<\/span>\u306f\u3001\u5f15\u6570\u306e\u30d7\u30ea\u30df\u30c6\u30a3\u30d6\u578b\u306e\u5024\u306b\u5bfe\u3059\u308b<span>hashCode<\/span>\u3092\u8fd4\u3059<span>static<\/span>\u30e1\u30bd\u30c3\u30c9\u3067\u3059\u3002\u5f15\u6570\u306e\u306a\u3044<span>hashCode<\/span>\u306f\u3001\u30d7\u30ea\u30df\u30c6\u30a3\u30d6\u578b\u306e\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u81ea\u8eab\u306e<span>hashCode<\/span>\u3092\u8fd4\u3059\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u30e1\u30bd\u30c3\u30c9\u3067\u3059\u3002<\/p>\n<pre class=\"prettyprint lang:default decode:true\">Double d = Double.valueOf(65535);\r\nSystem.out.println(d.hashCode()); \/\/ \u2192 1089470432\r\nSystem.out.println(Double.hashCode(65535)); \/\/ \u2192 1089470432<\/pre>\n<h4>\uff15-\uff11-\uff13\uff0e\u53c2\u7167\u578b\u306e\u30cf\u30c3\u30b7\u30e5\u5024\u306e\u8a08\u7b97\u65b9\u6cd5<\/h4>\n<p>\u53c2\u7167\u578b\u306e\u5834\u5408\u306f\u3001\u305d\u306e\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u304c\u6301\u3064<span>hashCode<\/span>\u304c\u623b\u3059\u30cf\u30c3\u30b7\u30e5\u5024\u3092\u4f7f\u3046\u306e\u304c\u539f\u5247\u3067\u3059\u3002\u305f\u3060\u3057\u3001\u305d\u306e\u30af\u30e9\u30b9\u304c<span>equals<\/span>\u3068\u9023\u52d5\u3057\u305f<span>hashCode<\/span>\u3092\u5b9f\u88c5\u3057\u3066\u3044\u308b\u304b\u306f\u78ba\u8a8d\u3057\u307e\u3057\u3087\u3046\u3002\u305d\u3046\u3067\u306a\u3044\u3068\u3001\u304a\u304b\u3057\u306a\u8a08\u7b97\u7d50\u679c\u306b\u306a\u3063\u3066\u3057\u307e\u3044\u307e\u3059\u3002<\/p>\n<p>\u5b9f\u969b\u306e\u8a08\u7b97\u306b\u306f\u3001<span>java.util.Objects<\/span>\u306e<span>static<\/span>\u30e1\u30bd\u30c3\u30c9<span>hashCode<\/span>\u3092\u4f7f\u3046\u3068\u3044\u3044\u3067\u3057\u3087\u3046\u3002<span>null<\/span>\u306e\u5834\u5408\u3082\u51e6\u7406\u3057\u3066\u304f\u308c\u307e\u3059\u306e\u3067\u3001\u81ea\u5206\u3067<span>if<\/span>\u6587\u3092\u66f8\u304b\u306a\u304f\u3066\u3082\u3044\u3044\u305f\u3081\u697d\u304c\u3067\u304d\u307e\u3059\u3002<\/p>\n<pre class=\"prettyprint lang:default decode:true\">String str1 = \"ABCD\";\r\nString str2 = null;\r\nSystem.out.println(Objects.hashCode(str1)); \/\/ \u2192 2001986\r\nSystem.out.println(Objects.hashCode(str2)); \/\/ \u2192 0<\/pre>\n<h4>\uff15-\uff11-\uff14\uff0e\u914d\u5217\u306e\u30cf\u30c3\u30b7\u30e5\u5024\u306e\u8a08\u7b97\u65b9\u6cd5<\/h4>\n<p>java.util.Arrays\u306e<span>hashCode<\/span>\u306f\u3001\u914d\u5217\u306e\u8981\u7d20\u3054\u3068\u306b<span>hashCode<\/span>\u3092\u5b9f\u884c\u3057\u3066\u3001\u5168\u4f53\u306e\u7d50\u679c\u3092\u623b\u3057\u3066\u304f\u308c\u307e\u3059\u3002\u914d\u5217\u306e\u578b\u3054\u3068\u306b\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3055\u308c\u305f\u30e1\u30bd\u30c3\u30c9\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<p>\u3061\u306a\u307f\u306b\u3001<span>Objects.hash<\/span>\u3092\u547c\u3073\u51fa\u3059\u3068\u3001<span>Java 11<\/span>\u306e\u5b9f\u88c5\u3067\u306f\u3053\u306e\u30e1\u30bd\u30c3\u30c9\u304c\u5b9f\u884c\u3055\u308c\u307e\u3059\u3002<\/p>\n<pre class=\"prettyprint lang:default decode:true\">boolean[] blArray = {true, false, true};\r\ndouble[] dblArray = {1.1, 2.2, 3.3};\r\nString[] strArray = {\"A\", \"B\", \"C\"};\r\n\r\nSystem.out.println(Arrays.hashCode(blArray)); \/\/ \u2192 1252360\r\nSystem.out.println(Arrays.hashCode(dblArray)); \/\/ \u2192 742162431\r\nSystem.out.println(Arrays.hashCode(strArray)); \/\/ \u2192 94369<\/pre>\n<p>java.util.Arrays\u306e<span>deepHashCode<\/span>\u306f\u3001\u914d\u5217\u306e\u8981\u7d20\u306e\u578b\u3092\u81ea\u52d5\u5224\u5b9a\u3057\u3066\u3001\u518d\u5e30\u7684\u306b<span>hashCode<\/span>\u3092\u8a08\u7b97\u3057\u3066\u304f\u308c\u307e\u3059\u3002\u4f8b\u3048\u3070\u3001\u4e8c\u6b21\u5143\u4ee5\u4e0a\u306e\u591a\u6b21\u5143\u914d\u5217\u3092\u6271\u3044\u305f\u3044\u5834\u5408\u3067\u3082\u5927\u4e08\u592b\u3067\u3059\u3002<\/p>\n<pre class=\"prettyprint lang:default decode:true\">double[][] dblArray = { { 1.1, 2.2, 3.3 }, { 4.4, 5.5, 6.6 } };\r\nString[][] strArray = { { \"A\", \"B\", \"C\" }, { \"D\", \"E\", \"F\" } };\r\nSystem.out.println(Arrays.deepHashCode(dblArray)); \/\/ \u2192 -603847868\r\nSystem.out.println(Arrays.deepHashCode(strArray)); \/\/ \u2192 3023748<\/pre>\n<h4>\uff15-\uff11-\uff15\uff0ehashCode\u306e\u5b9f\u88c5\u4f8b<\/h4>\n<p>\u3067\u306f\u8a66\u3057\u306b\u3001\u524d\u8ff0\u306e\u65b9\u6cd5\u3067<span>hashCode<\/span>\u3092\u5b9f\u88c5\u3057\u3066\u307f\u307e\u3059\u3002<\/p>\n<pre class=\"prettyprint lang:default decode:true\">import java.util.Arrays;\r\nimport java.util.Objects;\r\n\r\nclass HashCodeSample3 {\r\n\tboolean booleanField;\r\n\tbyte byteField;\r\n\tchar charField;\r\n\tshort shortField;\r\n\tint intField;\r\n\tlong longField;\r\n\tfloat floatField;\r\n\tdouble doubleField;\r\n\tString objectField;\r\n\tString[] arrayField;\r\n\r\n\tpublic int hashCode() {\r\n\t\tint result = 17; \/\/ \u8a08\u7b97\u7d50\u679c\u30010\u3067\u306f\u306a\u3044\u5024\u3067\u521d\u671f\u5316\u3059\u308b\r\n\t\tfinal int prime = 31; \/\/ \u8a08\u7b97\u3067\u4f7f\u3046\u5947\u6570\u306e\u7d20\u6570\r\n\r\n\t\tresult = prime * result + Boolean.hashCode(booleanField);\r\n\t\tresult = prime * result + Byte.hashCode(byteField);\r\n\t\tresult = prime * result + Character.hashCode(charField);\r\n\t\tresult = prime * result + Short.hashCode(shortField);\r\n\t\tresult = prime * result + Integer.hashCode(intField);\r\n\t\tresult = prime * result + Long.hashCode(longField);\r\n\t\tresult = prime * result + Float.hashCode(floatField);\r\n\t\tresult = prime * result + Double.hashCode(doubleField);\r\n\t\tresult = prime * result + Objects.hashCode(objectField);\r\n\t\tresult = prime * result + Arrays.hashCode(arrayField);\r\n\r\n\t\treturn result;\r\n\t}\r\n}<\/pre>\n<h3><span id=\"-Effective_JavahashCode\">\uff15-\uff12\uff0e\u3010\u53c2\u8003\u3011<span>Effective Java<\/span>\u3067\u306e<span>hashCode<\/span>\u8a08\u7b97\u65b9\u6cd5<\/span><\/h3>\n<p>\u6709\u540d\u306a<span>Java<\/span>\u306e\u672c\u300c<span>Effective Java<\/span>\u300d\u3067\u7d39\u4ecb\u3055\u308c\u3066\u3044\u308b<span>hashCode<\/span>\u8a08\u7b97\u306e\u65b9\u6cd5\u306f\u4ee5\u4e0b\u306e\u3082\u306e\u3067\u3059<span>(<\/span>\u3053\u308c\u306f\u7b2c\u4e8c\u7248\u306e\u3082\u306e<span>)<\/span>\u3002<\/p>\n<blockquote>\n<p>1.int result\u3092\u30010\u3067\u306a\u3044\u5b9a\u6570(\u4f8b:17)\u3067\u521d\u671f\u5316\u3059\u308b\u3002<br \/>\n2.\u30af\u30e9\u30b9\u5185\u306e\u30d5\u30a3\u30fc\u30eb\u30c9f(equals\u3067\u4f7f\u3046\u3082\u306e\u3059\u3079\u3066)\u3067\u4ee5\u4e0b\u306e\u8a08\u7b97\u3092\u3059\u308b\u3002<br \/>\n\u3000\u3000\u3000\u3000(a) f\u306e\u30cf\u30c3\u30b7\u30e5\u5024\u300cint c\u300d\u3092\u8a08\u7b97\u3059\u308b\u3002<br \/>\n\u3000\u3000\u3000\u3000\u3000\u3000\u3000i. boolean\u306a\u3089\u300c(f ? 0 : 1)\u300d\u306e\u7d50\u679c<br \/>\n\u3000\u3000\u3000\u3000\u3000\u3000\u3000ii. byte\/char\/short\/int\u306a\u3089\u300c(int)f\u300d\u306e\u7d50\u679c<br \/>\n\u3000\u3000\u3000\u3000\u3000\u3000\u3000iii. long\u306a\u3089\u300c(int)(f ^ (f &gt;&gt;&gt; 32))\u300d\u306e\u7d50\u679c<br \/>\n\u3000\u3000\u3000\u3000\u3000\u3000\u3000iv. float\u306a\u3089\u300cFloat.floatToIntBits(f)\u300d\u306e\u7d50\u679c<br \/>\n\u3000\u3000\u3000\u3000\u3000\u3000\u3000v. double \u306a\u3089\u300cDouble.doubelToLongBits(f)\u300d\u306elong\u3067\u30012 (a) iii\u3092\u3057\u305f\u7d50\u679c<br \/>\n\u3000\u3000\u3000\u3000\u3000\u3000\u3000vi. \u914d\u5217\u3067\u306f\u306a\u3044\u53c2\u7167\u578b\u5909\u6570\u306a\u3089\u300cf.hashCode()\u300d\u306e\u7d50\u679c(\u203b\u304d\u3061\u3093\u3068\u5b9f\u88c5\u3055\u308c\u3066\u3044\u305d\u3046\u306a\u3089)\u3002f\u304cnull\u306a\u30890\u3002<br \/>\n\u3000\u3000\u3000\u3000\u3000\u3000\u3000vii. \u914d\u5217\u306a\u3089\u3001\u5404\u8981\u7d20\u3092\u5225\u3005\u306e\u30d5\u30a3\u30fc\u30eb\u30c9\u3068\u3057\u3066i\uff5ev\u3092\u884c\u3063\u305f\u7d50\u679c<br \/>\n\u3000\u3000\u3000\u3000(b) c\u3092\u300cresult = 31 * result + c\u300d\u3068\u3057\u3066\u7d50\u679c\u306b\u6df7\u305c\u8fbc\u3080<\/p>\n<\/blockquote>\n<p>\u3061\u306a\u307f\u306b\u3001\u300c<span>31<\/span>\u300d\u3068\u3044\u3046\u8b0e\u306e\u6570\u5b57\u304c\u3044\u304d\u306a\u308a\u51fa\u3066\u3044\u307e\u3059\u3057\u3001\u305d\u306e\u6570\u5b57\u3092\u4f7f\u3063\u3066\u306a\u305c\u304b\u639b\u3051\u7b97\u3092\u3057\u3066\u3044\u307e\u3059\u3002\u524d\u8ff0\u3057\u305f<span>Java<\/span>\u6a19\u6e96<span>API<\/span>\u3067\u306e\u8a08\u7b97\u65b9\u6cd5\u306b\u51fa\u3066\u304d\u305f\u6570\u5b57<span>31<\/span>\u3084\u8a08\u7b97\u5f0f\u3082\u3001\u3053\u308c\u304c\u5143\u30cd\u30bf\u3060\u3063\u305f\u308a\u3057\u307e\u3059\u3002<\/p>\n<p>\u3053\u308c\u3089\u306e\u6570\u5b57\u3084\u8a08\u7b97\u65b9\u6cd5\u306b\u306f\u3001\u306a\u304b\u306a\u304b\u6df1\u9060\u306a\u7406\u7531\u304c\u3042\u308b\u306e\u3067\u3059\u3002\u8208\u5473\u304c\u3042\u308c\u3070\u3001\u30cf\u30c3\u30b7\u30e5\u30b3\u30fc\u30c9\u306e\u8a08\u7b97\u65b9\u6cd5\u306b\u3064\u3044\u3066\u8abf\u3079\u3066\u307f\u3066\u3082\u3044\u3044\u3067\u3057\u3087\u3046\u3002<\/p>\n<p>\u306a\u304a\u3001<span>Java<\/span>\u6a19\u6e96<span>API<\/span>\u3067\u306e\u5b9f\u88c5\u3082\u3001\u6982\u306d\u3053\u308c\u3068\u540c\u3058\u3067\u3059\u3002\u305f\u3060\u3057\u3001\u7d30\u304b\u3044\u3068\u3053\u308d\u306f\u9055\u3063\u3066\u3044\u307e\u3059\u3002<\/p>\n<h2><span id=\"hashCode-4\">\uff16\uff0e\u3010\u767a\u5c55\u3011<span>hashCode<\/span>\u306e\u3042\u308c\u3053\u308c<\/span><\/h2>\n<h3><span id=\"-hashCode-2\">\uff16-\uff11\uff0ehashCode\u306f\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3059\u308b\u3082\u306e<\/span><\/h3>\n<p>Object.hashCode\u306f\u3001\u30b5\u30d6\u30af\u30e9\u30b9\u3067\u9069\u5207\u306b\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9<span>(override)<\/span>\u3057\u306a\u3051\u308c\u3070\u306a\u308a\u307e\u305b\u3093\u3002\u9055\u3046\u5f15\u6570\u3092\u6301\u3063\u305f\u30e1\u30bd\u30c3\u30c9\u3092\u4f5c\u3063\u3066\u30aa\u30fc\u30d0\u30fc\u30ed\u30fc\u30c9<span>(overload)<\/span>\u3057\u3066\u3082\u3001\u671f\u5f85\u3057\u305f\u3068\u304a\u308a\u306e\u52d5\u304d\u306b\u306f\u306a\u308a\u307e\u305b\u3093\u306e\u3067\u3001\u6c17\u3092\u4ed8\u3051\u307e\u3057\u3087\u3046\u3002<\/p>\n<h3><span id=\"-hashCode-3\">\uff16-\uff12\uff0ehashCode\u3092\u81ea\u52d5\u751f\u6210\u3057\u3066\u697d\u3092\u3059\u308b<\/span><\/h3>\n<p>hashCode\u306e\u8a08\u7b97\u3067\u4f7f\u3046\u30d5\u30a3\u30fc\u30eb\u30c9\u304c\u5897\u3048\u3066\u304f\u308b\u3068\u3001\u305d\u308c\u3089\u306e\u30d5\u30a3\u30fc\u30eb\u30c9\u3092\u8a08\u7b97\u9014\u4e2d\u306b\u304d\u3061\u3093\u3068\u5165\u308c\u3066\u3001\u52d5\u4f5c\u78ba\u8a8d\u3092\u3059\u308b\u3060\u3051\u3067\u3082\u4e00\u82e6\u52b4\u3067\u3059\u3002\u3067\u3059\u304c\u3001<span>IDE<\/span>\u3084\u30e9\u30a4\u30d6\u30e9\u30ea\u3092\u4e0a\u624b\u306b\u4f7f\u3046\u3068\u3001\u304d\u3061\u3093\u3068\u3057\u305f<span>hashCode<\/span>\u3092\u7c21\u5358\u306b\u81ea\u52d5\u751f\u6210\u3067\u304d\u305f\u308a\u3059\u308b\u306e\u3067\u3059<span>!! <\/span>\u3053\u3053\u3067\u5b66\u3093\u3067\u3001\u305c\u3072\u3069\u3093\u3069\u3093\u6d3b\u7528\u3057\u307e\u3057\u3087\u3046\u3002<\/p>\n<h4>\uff16-\uff12-\uff11\uff0eIDE\u306e\u6a5f\u80fd\u3092\u4f7f\u3046<\/h4>\n<p>Eclipse\u3001<span>IntelliJ IDEA<\/span>\u3001<span>NetBeans<\/span>\u306a\u3069\u306e<span>Java<\/span>\u5411\u3051<span>IDE<\/span>\u3067\u306f\u3001<span>hashCode<\/span>\u3092\u81ea\u52d5\u751f\u6210\u3057\u3066\u304f\u308c\u308b\u6a5f\u80fd\u304c\u3042\u308a\u307e\u3059\u3002\u3053\u3053\u3067\u306f<span>Eclipse<\/span>\u3067\u306e\u4f8b\u3092\u793a\u3057\u307e\u3059\u3002<\/p>\n<p>\u4f8b\u3048\u3070\u3001\u4ee5\u4e0b\u306e\u3088\u3046\u306a\u30af\u30e9\u30b9\u304c\u3042\u3063\u305f\u3068\u3057\u307e\u3059\u3002\u3053\u306e\u30af\u30e9\u30b9\u306b<span>Eclipse<\/span>\u3067<span>equals<\/span>\u3092\u81ea\u52d5\u751f\u6210\u3057\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n<pre class=\"prettyprint lang:default decode:true\">class HashCodeSample4 {\r\n\tint intField;\r\n\tString objField;\r\n}<\/pre>\n<p>\u3053\u306e\u30af\u30e9\u30b9\u3092\u30d1\u30c3\u30b1\u30fc\u30b8\u30a8\u30af\u30b9\u30d7\u30ed\u30fc\u30e9\u306a\u3069\u304b\u3089\u3001\u300c\u53f3\u30af\u30ea\u30c3\u30af\u300d<span>\u2192<\/span>\u300c\u30bd\u30fc\u30b9\u300d<span>\u2192<\/span>\u300c<span>hashCode()<\/span>\u304a\u3088\u3073<span>equals()<\/span>\u306e\u751f\u6210\u300d\u3092\u9078\u3073\u307e\u3059\u3002\u3059\u308b\u3068\u300c<span>hashCode()<\/span>\u304a\u3088\u3073<span>equals()<\/span>\u306e\u751f\u6210\u300d\u30a6\u30a3\u30b6\u30fc\u30c9\u304c\u8868\u793a\u3055\u308c\u308b\u306e\u3067\u3001<span>equals<\/span>\u3068<span>hashCode<\/span>\u306e\u5bfe\u8c61\u3068\u3057\u305f\u3044\u30d5\u30a3\u30fc\u30eb\u30c9\u3092\u9078\u3073\u3001<span>OK<\/span>\u30dc\u30bf\u30f3\u3092\u62bc\u3057\u307e\u3059\u3002<\/p>\n<p>\u3059\u308b\u3068\u3001\u4ee5\u4e0b\u306e\u3088\u3046\u306b<span>equals<\/span>\u3068<span>hashCode<\/span>\u304c\u81ea\u52d5\u751f\u6210\u3055\u308c\u307e\u3057\u305f\u3002\u5c11\u3005\u3054\u3061\u3083\u3054\u3061\u3083\u3057\u305f\u30bd\u30fc\u30b9\u30b3\u30fc\u30c9\u3067\u3059\u304c\u3001\u304d\u3061\u3093\u3068\u52d5\u304d\u307e\u3059\u3002\u305d\u308c\u306b\u3001\u5b9f\u88c5\u3057\u3065\u3089\u3044<span>hashCode<\/span>\u3082<span>equals<\/span>\u3068\u540c\u671f\u3092\u53d6\u3063\u3066\u751f\u6210\u3057\u3066\u304f\u308c\u308b\u306e\u306f\u3001\u5927\u5909\u52a9\u304b\u308a\u307e\u3059\u306d\u3002<\/p>\n<pre class=\"prettyprint lang:default decode:true\">class HashCodeSample4 {\r\n\tint intField;\r\n\tString objField;\r\n\r\n\t@Override\r\n\tpublic int hashCode() {\r\n\t\tfinal int prime = 31;\r\n\t\tint result = 1;\r\n\t\tresult = prime * result + intField;\r\n\t\tresult = prime * result + ((objField == null) ? 0 : objField.hashCode());\r\n\t\treturn result;\r\n\t}\r\n\r\n\t@Override\r\n\tpublic boolean equals(Object obj) {\r\n\t\tif (this == obj)\r\n\t\t\treturn true;\r\n\t\tif (obj == null)\r\n\t\t\treturn false;\r\n\t\tif (getClass() != obj.getClass())\r\n\t\t\treturn false;\r\n\t\tHashCodeSample4 other = (HashCodeSample4) obj;\r\n\t\tif (intField != other.intField)\r\n\t\t\treturn false;\r\n\t\tif (objField == null) {\r\n\t\t\tif (other.objField != null)\r\n\t\t\t\treturn false;\r\n\t\t} else if (!objField.equals(other.objField))\r\n\t\t\treturn false;\r\n\t\treturn true;\r\n\t}\r\n}<\/pre>\n<blockquote>\n<p>\u3010\u53c2\u8003\u3011<\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 IntelliJ IDEA\u306e\u81ea\u52d5\u751f\u6210\u30a6\u30a3\u30b6\u30fc\u30c9<\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<a href=\"https:\/\/www.jetbrains.com\/help\/idea\/generate-equals-and-hashcode-wizard.html\"> https:\/\/www.jetbrains.com\/help\/idea\/generate-equals-and-hashcode-wizard.html<\/a><\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u2192[\u82f1\u8a9e<span>]IntelliJ IDEA<\/span>\u306e\u8a72\u5f53\u90e8\u5206\u306e\u30de\u30cb\u30e5\u30a2\u30eb\u3067\u3059\u3002<\/p>\n<p>&nbsp;<\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 NetBeans\u3067\u306e\u81ea\u52d5\u751f\u6210\u624b\u9806<\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <a href=\"https:\/\/blogs.oracle.com\/java\/ten-time-savers-in-netbeans-v2\" class=\"broken_link\">https:\/\/blogs.oracle.com\/java\/ten-time-savers-in-netbeans-v2<\/a><\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u2192[\u82f1\u8a9e<span>]<\/span>\u300c<span>Number 2: Auto-generate getters and setters, constructors and more!<\/span>\u300d\u306e\u3068\u3053\u308d\u306b\u624b\u9806\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n<p>&nbsp;<\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <a href=\"https:\/\/stackoverflow.com\/questions\/38242576\/can-netbeans-auto-generate-correct-hashcode-and-equals-methods-for-a-mapping\">https:\/\/stackoverflow.com\/questions\/38242576\/can-netbeans-auto-generate-correct-hashcode-and-equals-methods-for-a-mapping<\/a><\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u2192[\u82f1\u8a9e<span>]equals<\/span>\u3092\u81ea\u52d5\u3059\u308b\u64cd\u4f5c\u306e\u7c21\u5358\u306a\u624b\u9806\u304c\u7d39\u4ecb\u3055\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n<p>&nbsp;<\/p>\n<\/blockquote>\n<h4>\uff16-\uff12-\uff12\uff0e\u30e9\u30a4\u30d6\u30e9\u30ea\u3092\u4f7f\u3046<span>(Lombok<\/span>\u306a\u3069<span>)<\/span><\/h4>\n<p>hashCode\u306f<span>IDE<\/span>\u306b\u81ea\u52d5\u751f\u6210\u3055\u305b\u308b\u4ee5\u5916\u306b\u3082\u3001\u5916\u90e8\u30e9\u30a4\u30d6\u30e9\u30ea\u3092\u4f7f\u3063\u3066\u81ea\u52d5\u751f\u6210\u3059\u308b\u65b9\u6cd5\u3082\u3042\u308a\u307e\u3059\u3002\u4ee3\u8868\u7684\u306a\u306e\u306f\u3001<span>Lombok<\/span>\u3068\u3044\u3046\u30e9\u30a4\u30d6\u30e9\u30ea\u3092\u4f7f\u3046\u3053\u3068\u3067\u3059\u3002<\/p>\n<p>Lombok\u306e\u8a73\u7d30\u3084\u4f7f\u3048\u308b\u3088\u3046\u306b\u3059\u308b\u624b\u9806\u306f\u7701\u304d\u307e\u3059\u304c\u3001\u4ee5\u4e0b\u306e\u3088\u3046\u306b\u30af\u30e9\u30b9\u3078\u30a2\u30ce\u30c6\u30fc\u30b7\u30e7\u30f3\u300c<span>@EqualsAndHashCode<\/span>\u300d\u3092\u4ed8\u3051\u308b\u3060\u3051\u3067\u3001\u30af\u30e9\u30b9\u306b\u3042\u308b\u30d5\u30a3\u30fc\u30eb\u30c9\u3092\u4f7f\u3063\u305f<span>equals<\/span>\u3068<span>hashCode<\/span>\u3092\u81ea\u52d5\u7684\u306b\u4f5c\u3063\u3066\u304f\u308c\u307e\u3059<span>!!(\u203b) <\/span>\u3082\u306e\u3059\u3054\u304f\u697d\u3061\u3093\u3067\u3059\u306d\u3002<\/p>\n<p>\u203bJava\u306e\u30bd\u30fc\u30b9\u30b3\u30fc\u30c9\u4e0a\u306b\u306f<span>equals<\/span>\u3068<span>hashCode<\/span>\u306f\u4f5c\u6210\u3055\u308c\u305a\u3001\u30b3\u30f3\u30d1\u30a4\u30eb\u3057\u305f\u7d50\u679c\u306e\u30af\u30e9\u30b9\u30d5\u30a1\u30a4\u30eb<span>(.class)<\/span>\u306e\u4e2d\u3060\u3051\u306b\u3001\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3055\u308c\u305f\u30e1\u30bd\u30c3\u30c9\u306e\u5b9f\u88c5\u304c\u81ea\u52d5\u7684\u306b\u542b\u307e\u308c\u307e\u3059\u3002<\/p>\n<pre class=\"prettyprint lang:default decode:true\">import lombok.EqualsAndHashCode;\r\n\r\n@EqualsAndHashCode\r\npublic class HashCodeHashCodeSample5 {\r\n\tint intField;\r\n\tString objField;\r\n}<\/pre>\n<blockquote>\n<p>\u3010\u53c2\u8003\u3011<\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Project Lombok<\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <a href=\"https:\/\/projectlombok.org\/\">https:\/\/projectlombok.org\/<\/a><\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u2192[\u82f1\u8a9e<span>]<\/span>\u30d7\u30ed\u30b8\u30a7\u30af\u30c8\u306e<span>WEB<\/span>\u30da\u30fc\u30b8\u3067\u3059<\/p>\n<p>&nbsp;<\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 @EqualsAndHashCode<\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<a href=\"https:\/\/projectlombok.org\/features\/EqualsAndHashCode\"> https:\/\/projectlombok.org\/features\/EqualsAndHashCode<\/a><\/p>\n<p>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u2192[\u82f1\u8a9e<span>]<\/span>\u516c\u5f0f<span>WEB<\/span>\u30da\u30fc\u30b8\u5185\u306e\u3001<span>@EqualsAndHashCode<\/span>\u306e\u8aac\u660e\u30da\u30fc\u30b8\u3067\u3059\u3002<\/p>\n<\/blockquote>\n<h2><span id=\"i\">\uff17\uff0e\u3055\u3044\u3054\u306b<\/span><\/h2>\n<p>\u3053\u306e\u8a18\u4e8b\u3067\u306f\u3001<span>Object.hashCode<\/span>\u3092\u8aac\u660e\u3057\u3066\u304d\u307e\u3057\u305f\u3002<span>hashCode<\/span>\u3092\u4f7f\u3046\u3068\u3001\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u3092\u8868\u3059\u30cf\u30c3\u30b7\u30e5\u5024\u304c\u5f97\u3089\u308c\u307e\u3059\u3002<\/p>\n<p>\u3042\u306a\u305f\u304c\u4f5c\u3063\u305f\u30af\u30e9\u30b9\u3067<span>hashCode<\/span>\u3092<span>equals<\/span>\u3068\u4f75\u305b\u3066\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3057\u3066\u3044\u306a\u3044\u3068\u3001<span>HashMap<\/span>\u3084<span>HashSet<\/span>\u304c\u4e0a\u624b\u304f\u52d5\u304d\u307e\u305b\u3093\u3002<span>equals<\/span>\u3092\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3057\u305f\u6642\u306f\u3001\u5fd8\u308c\u305a\u306b<span>hashCode<\/span>\u3082\u30aa\u30fc\u30d0\u30fc\u30e9\u30a4\u30c9\u3057\u307e\u3057\u3087\u3046\u306d\u3002<\/p>\n<p>equals\u3068<span>hashCode<\/span>\u3092\u6b63\u3057\u304f\u4f5c\u308c\u3070\u3001<span>Java<\/span>\u306e\u6a19\u6e96<span>API<\/span>\u306b\u3042\u308b\u8272\u3005\u306a\u30af\u30e9\u30b9\u3092\u3001\u6b63\u3057\u304f\u4fbf\u5229\u306b\u4f7f\u3048\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002\u5c11\u3057\u96e3\u3057\u3044\u8003\u3048\u65b9\u304c\u6c42\u3081\u3089\u308c\u308b\u3068\u3053\u308d\u3082\u3042\u308a\u307e\u3059\u304c\u3001\u3057\u3063\u304b\u308a\u3068\u30dd\u30a4\u30f3\u30c8\u3092\u62bc\u3055\u3048\u3066\u6d3b\u7528\u3067\u304d\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3057\u3087\u3046\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Object.hashCode\u306f\u3001\u547c\u3073\u51fa\u3055\u308c\u305f\u30a4\u30f3\u30b9\u30bf\u30f3\u30b9\u306e\u7279\u5fb4\u3092\u8868\u3059\u300c\u30cf\u30c3\u30b7\u30e5\u5024\u300d\u3092\u8fd4\u3059\u30e1\u30bd\u30c3\u30c9\u3067\u3059\u3002 \u3053\u306e\u30cf\u30c3\u30b7\u30e5\u5024\u306fHashMap\u3084HashSet\u306a\u3069\u306eJava\u6a19\u6e96API\u306b\u3042\u308b\u30af\u30e9\u30b9\u306e\u591a\u304f\u3067\u4f7f\u308f\u308c\u307e\u3059\u3002 \u305d\u3057\u3066\u3001h [&hellip;]<\/p>\n","protected":false},"author":3,"featured_media":804,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[14],"acf":[],"_links":{"self":[{"href":"https:\/\/www.bold.ne.jp\/engineer-club\/wp-json\/wp\/v2\/posts\/1372"}],"collection":[{"href":"https:\/\/www.bold.ne.jp\/engineer-club\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bold.ne.jp\/engineer-club\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bold.ne.jp\/engineer-club\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bold.ne.jp\/engineer-club\/wp-json\/wp\/v2\/comments?post=1372"}],"version-history":[{"count":8,"href":"https:\/\/www.bold.ne.jp\/engineer-club\/wp-json\/wp\/v2\/posts\/1372\/revisions"}],"predecessor-version":[{"id":5772,"href":"https:\/\/www.bold.ne.jp\/engineer-club\/wp-json\/wp\/v2\/posts\/1372\/revisions\/5772"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.bold.ne.jp\/engineer-club\/wp-json\/wp\/v2\/media\/804"}],"wp:attachment":[{"href":"https:\/\/www.bold.ne.jp\/engineer-club\/wp-json\/wp\/v2\/media?parent=1372"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bold.ne.jp\/engineer-club\/wp-json\/wp\/v2\/categories?post=1372"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}