{"id":27150,"date":"2020-07-17T19:39:55","date_gmt":"2020-07-17T10:39:55","guid":{"rendered":"https:\/\/vitalify.jp\/blog\/?p=27150"},"modified":"2024-04-26T14:22:20","modified_gmt":"2024-04-26T05:22:20","slug":"nomore_switch","status":"publish","type":"post","link":"https:\/\/vitalify.jp\/blog\/2020\/07\/nomore_switch.html","title":{"rendered":"\u3010Java\u3011\u30e9\u30e0\u30c0\u5f0f\u304c\u3042\u308c\u3070switch\u3044\u3089\u306a\u3044\u3093\u3058\u3083\u306d\uff1f"},"content":{"rendered":"

\u3053\u3093\u306b\u3061\u306f\u3001
\n\u30b3\u30fc\u30d2\u30fc\u306f\u4e00\u65e5\u4e00\u676f\u307e\u3067\u3002\u795e\u5c3e\u3067\u3059\u3002<\/p>\n

switch\u6587\u304c\u5acc\u3044\u306a\u30d7\u30ed\u30b0\u30e9\u30de\u30fc\u306f\u591a\u3044\u3068\u601d\u3044\u307e\u3059\u3002
\n<\/p>\n

Java\u306eswitch\u306f\u5217\u6319\u578b\u6bd4\u8f03(\u203b)\u306a\u306e\u3067php\u3068\u6bd4\u3079\u305f\u3089\u5168\u7136\u307e\u3057\u3067\u3059\u3051\u3069\u3001
\n\u3057\u304b\u3057\u4f55\u3068\u3082\u3044\u3048\u306a\u3044\u3053\u306e\u98df\u3044\u5408\u308f\u305b\u306e\u60aa\u3055\u3002<\/p>\n

break\u306e\u4ed8\u3051\u5fd8\u308c\u3067\u30d0\u30b0\u3002
\n\u30a4\u30f3\u30c7\u30f3\u30c8\u304c\u898b\u306b\u304f\u3044\u3002<\/p>\n

\u3042\u3068\u3001\u300cswitch-case\u6587\u300d\u3068\u304b\u3044\u3046\u3051\u3069\u3001\u6587\u306fswitch\u3060\u3051\u3067\u3001case\u3001\u8cb4\u69d8\u306f\u305f\u3060\u306e\u30e9\u30d9\u30eb\u3060\u3002<\/p>\n

\u306a\u306e\u3067\u4eca\u65e5\u306f\u666e\u6bb5\u3042\u3093\u307e\u308a\u4f7f\u308f\u306a\u3044\u30e9\u30e0\u30c0\u5f0f\u3092\u4f7f\u3063\u3066\u3001
\nswitch\u6587\u307f\u305f\u3044\u306a\u30af\u30e9\u30b9\u3092\u4f5c\u308b\u3088\u3002<\/p>\n

\"\"<\/p>\n

\u203b\u5217\u6319\u578b…enum\u3068\u3082\u3044\u3046\u3002\u5b9a\u6570\u306e\u914d\u5217\u307f\u305f\u3044\u306a\u4f55\u304b\u3002
\nswitch\u3067\u306f\u3001String\u306e\u3088\u3046\u306b\u898b\u3048\u3066\u3082\u5217\u6319\u578b\u306b\u30b3\u30f3\u30d1\u30a4\u30eb\u3055\u308c\u3066\u3044\u308b\u3002
\nnull\u3092\u7a81\u3063\u8fbc\u3080\u3068\u30a8\u30e9\u30fc\u306b\u306a\u308b\u306e\u306f\u305d\u306e\u305b\u3044\u3002<\/p>\n

Switch\u30af\u30e9\u30b9\u4f5c\u3063\u3066\u307f\u305f<\/h2>\n
import java.util.function.Consumer;\r\n\r\npublic class Switch<T, R> {\r\n    private T comparison;\r\n    private R controlee;\r\n    private boolean end;\r\n\r\n    private Switch(T comparison, R controlee) {\r\n        this.comparison = comparison;\r\n        this.controlee = controlee;\r\n    }\r\n\r\n    private void consume(Consumer<R> consumer) {\r\n        if(!end) {\r\n            if(consumer != null) {\r\n                consumer.accept(controlee);\r\n            }\r\n            end = true;\r\n        }\r\n    }\r\n\r\n    public static <T, R> Switch swit(T comparison, R controlee) {\r\n        Switch swit = new Switch<T, R>(comparison, controlee);\r\n        swit.init();\r\n        return swit;\r\n    }\r\n\r\n    public void init() {\r\n        end = false;\r\n    }\r\n\r\n    public Switch when(T target, Consumer<R> consumer) {\r\n        if(target.equals(comparison)) {\r\n            consume(consumer);\r\n        }\r\n        return this;\r\n    }\r\n\r\n    public Switch defa(Consumer<R> consumer) {\r\n        consume(consumer);\r\n        return this;\r\n    }\r\n\r\n}<\/code><\/pre>\n
\u4f55\u304b\u3042\u3093\u307e\u308a\u304b\u3063\u3053\u3088\u304f\u306a\u3044\u3051\u3069\u3001\u30b3\u30f3\u30d1\u30a4\u30eb\u901a\u3063\u305f\u304b\u3089\u3044\u3044\u304b\u3002<\/p>\n
\u30e9\u30e0\u30c0\u578b\u306e1\u3064\u3067\u3042\u308bConsumer<\/a>\u3092\u4f7f\u3063\u3066\u3044\u307e\u3059\u3002<\/p>\n
\u30e9\u30e0\u30c0\u578b\u306f\u62bd\u8c61\u30e1\u30bd\u30c3\u30c9\u304c1\u3064\u3060\u3051\u306e\u30a4\u30f3\u30bf\u30fc\u30d5\u30a7\u30fc\u30b9\u306e\u3053\u3068\u3002
\n\u4ee3\u8868\u7684\u306a\u306e\u306fRunnable\u3060\u3051\u3069\u3001\u3053\u308c\u306f\u5f15\u6570\u3082\u623b\u308a\u5024\u3082\u306a\u3044\u3001\u8d70\u308b\u3057\u304b\u3067\u304d\u3093\u5b50\u3002<\/p>\n
java.util.function\u30d1\u30c3\u30b1\u30fc\u30b8<\/a>\u306b\u306f\u30e9\u30e0\u30c0\u578b\u304c\u3044\u308d\u3044\u308d\u5165\u3063\u3066\u308b\u304b\u3089\u3001
\n\u5f15\u6570\u3084\u623b\u308a\u5024\u306e\u6570\u306b\u3088\u3063\u3066\u597d\u304d\u306a\u306e\u3092\u9078\u3076\u3068\u3044\u3044\u3088\u3001\u3063\u3066\u611f\u3058\u3002<\/p>\n
\u8a73\u3057\u304f\u306f\u3053\u3061\u3089\u3002<\/a><\/p>\n
\u4f7f\u3044\u65b9<\/h2>\n
class Test {\r\n\r\n    public static void main(String args[]){\r\n        String bread = \"croissant\";\r\n        BreadEater breadEater = new BreadEater();\r\n\r\n        Switch.swit(bread, breadEater)\r\n                .when(\"shokupan\", (obj)->{\r\n                    obj.message(\"mochi mochi\");\r\n                })\r\n                .when(\"coupe\", (obj)->{\r\n                    obj.message(\"fuwa fuwa\");\r\n                })\r\n                .when(\"croissant\", (obj)->{\r\n                    obj.message(\"saku saku\");\r\n                })\r\n                .defa((obj)->{\r\n                    obj.message(\"hara hetta\");\r\n                });\r\n\r\n        breadEater.talk();\r\n    }\r\n\r\n    static class BreadEater {\r\n        private String message;\r\n\r\n        void message(String message) {\r\n            this.message = message;\r\n        }\r\n\r\n        void talk() {\r\n            System.out.println(message);\r\n        }\r\n    }\r\n\r\n}<\/code><\/pre>\n
(obj)->{
\n  \/\/\u51e6\u7406
\n}
\n\u306e\u90e8\u5206\u304c\u30e9\u30e0\u30c0\u5f0f\u3002
\n\u4f7f\u3044\u6163\u308c\u306a\u3044\u3051\u3069\u3001\u7121\u540d\u30af\u30e9\u30b9\u306e\u5ba3\u8a00\u3092\u7701\u7565\u3057\u3066\u308b\u3060\u3051\u3002<\/p>\n
\u7121\u540d\u30af\u30e9\u30b9\u3082\u540c\u3058\u3060\u3051\u3069\u3001\u30e9\u30e0\u30c0\u5f0f\u306e\u4e2d\u3067\u306f\u30e9\u30e0\u30c0\u5f0f\u306e\u5916\u3067\u5ba3\u8a00\u3055\u308c\u305ffinal\u4ee5\u5916\u306e\u30ed\u30fc\u30ab\u30eb\u95a2\u6570\u306f\u4f7f\u3048\u306a\u3044\u3002
\n\u3060\u304b\u3089\u51e6\u7406\u7528\u306e\u30af\u30e9\u30b9\u3092\u7528\u610f\u3057\u3066\u3001Consumer\u306b\u6e21\u3057\u3066\u3044\u308b\u3002<\/p>\n
\u306a\u3093\u3060\u304b\u3082\u3046\u5341\u5206\u307e\u3069\u308d\u3063\u3053\u3057\u3044\u3051\u3069\u3001\u30b3\u30f3\u30d1\u30a4\u30e9\u306f\u901a\u3089\u306a\u3044\u3002<\/p>\n
Test.java:9: \u30a8\u30e9\u30fc: \u30bf\u30a4\u30d7Object\u306emessage(String)\u3092\u898b\u3064\u3051\u3089\u308c\u307e\u305b\u3093\r\n                    obj.message(\"mochi mochi\");\r\n                       ^\r\n<\/code><\/pre>\n
\u3048\u30fc\uff1f\u306a\u3093\u3067Object\u3067Consumer\u306b\u6e21\u3063\u3066\u308b\u306e\uff1f
\n\u578b\u5ba3\u8a00\u3057\u306a\u304b\u3063\u305f\u304b\u3089\u30fb\u30fb\u30fb\uff1f<\/p>\n
        Switch.swit(bread, breadEater)\r\n\u21d3\r\n        Switch.<String, BreadEater>swit(bread, breadEater)\r\n<\/code><\/pre>\n
\u30b8\u30a7\u30cd\u30ea\u30c3\u30af\u30e1\u30bd\u30c3\u30c9\u3067\u3042\u308bswit\u3092\u3001\u660e\u793a\u7684\u306b\u578b\u5ba3\u8a00\u3057\u3066\u5b9f\u884c\u3002
\n\u3067\u3082\u3001\u3053\u308c\u3082\u3060\u3081\u3002<\/p>\n
\u3057\u3087\u3046\u304c\u306a\u3044\u306e\u3067\u3001\u6700\u7d42\u7684\u306b\u3053\u3046\u306a\u3063\u305f\u3002<\/p>\n
        Switch.swit(bread, breadEater)\r\n                .when(\"shokupan\", (obj)->{\r\n                    ((BreadEater)obj).message(\"mochi mochi\");\r\n                })\r\n                .when(\"coupe\", (obj)->{\r\n                    ((BreadEater)obj).message(\"fuwa fuwa\");\r\n                })\r\n                .when(\"croissant\", (obj)->{\r\n                    ((BreadEater)obj).message(\"saku saku\");\r\n                })\r\n                .defa((obj)->{\r\n                    ((BreadEater)obj).message(\"hara hetta\");\r\n                });\r\n<\/code><\/pre>\n
\u3061\u3083\u3093\u3068\u52d5\u3044\u305f\u3051\u3069\u3001\u30ab\u30c3\u30b3\u60aa\u3044\u306a\u3042\u3002<\/p>\n
\u3084\u3063\u3071\u308aswitch\u4f7f\u304a\u3046\u304b\u306a\u3042\u3001\u30c8\u30db\u30db\u3002<\/p>\n
\u8ffd\u8a18<\/h2>\n
\u30e1\u30bd\u30c3\u30c9\u306e\u623b\u308a\u5024\u306b\u30b8\u30a7\u30cd\u30ea\u30c3\u30af\u306e\u578b\u3092\u6307\u5b9a\u3059\u308b\u306e\u3092\u5fd8\u308c\u3066\u307e\u3057\u305f\uff01\uff01<\/p>\n
-    public static <T, R> Switch swit(T comparison, R controlee) {\r\n+    public static <T, R> Switch<T, R> swit(T comparison, R controlee) {\r\n\r\n---\r\n\r\n-    public Switch when(T target, Consumer consumer) {\r\n+    public Switch<T, R> when(T target, Consumer consumer) {\r\n\r\n---\r\n\r\n-    public Switch defa(Consumer consumer) {\r\n+    public Switch<T, R> defa(Consumer consumer) {\r\n<\/code><\/pre>\n
\u3053\u308c\u3067\u30d0\u30c3\u30c1\u30ea\u3002<\/p>\n
\n            
<\/div><\/fb:like><\/div>\n            
<\/g:plusone><\/div>\n            
 \"\u3053\u306e\u30a8\u30f3\u30c8\u30ea\u30fc\u3092\u306f\u3066\u306a\u30d6\u30c3\u30af\u30de\u30fc\u30af\u306b\u8ffd\u52a0\"<\/a>