{"id":10006933,"date":"2022-11-29T14:11:44","date_gmt":"2022-11-29T06:11:44","guid":{"rendered":"https:\/\/ityet.com\/?p=10006933"},"modified":"2022-11-29T14:11:44","modified_gmt":"2022-11-29T06:11:44","slug":"function%e6%ba%90%e7%a0%81%e8%a7%a3%e6%9e%90%e4%b8%8e%e5%ae%9e%e8%b7%b5","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10006933","title":{"rendered":"Function\u6e90\u7801\u89e3\u6790\u4e0e\u5b9e\u8df5"},"content":{"rendered":"

\u4f5c\u8005\uff1a\u9648\u660c\u6d69<\/h2>\n

1 \u5bfc\u8bfb<\/h3>\n

if\u2026else\u2026\u5728\u4ee3\u7801\u4e2d\u7ecf\u5e38\u4f7f\u7528\uff0c\u542c\u8bf4\u53ef\u4ee5\u901a\u8fc7Java 8\u7684Function\u63a5\u53e3\u6765\u6d88\u706dif\u2026else\u2026\uff01Function\u63a5\u53e3\u662f\u4ec0\u4e48\uff1f\u5982\u679c\u901a\u8fc7Function\u63a5\u53e3\u63a5\u53e3\u6d88\u706dif\u2026else\u2026\u5462\uff1f\u8ba9\u6211\u4eec\u4e00\u8d77\u6765\u63a2\u7d22\u4e00\u4e0b\u5427\u3002<\/p>\n

2 Function\u63a5\u53e3<\/h3>\n

Function\u63a5\u53e3\u5c31\u662f\u4e00\u4e2a\u6709\u4e14\u4ec5\u6709\u4e00\u4e2a\u62bd\u8c61\u65b9\u6cd5\uff0c\u4f46\u662f\u53ef\u4ee5\u6709\u591a\u4e2a\u975e\u62bd\u8c61\u65b9\u6cd5\u7684\u63a5\u53e3,Function\u63a5\u53e3\u53ef\u4ee5\u88ab\u9690\u5f0f\u8f6c\u6362\u4e3a lambda \u8868\u8fbe\u5f0f\u3002\u53ef\u4ee5\u901a\u8fc7FunctionalInterface\u6ce8\u89e3\u6765\u6821\u9a8cFunction\u63a5\u53e3\u7684\u6b63\u786e\u6027\u3002Java 8\u5141\u8bb8\u5728\u63a5\u53e3\u4e2d\u52a0\u5165\u5177\u4f53\u65b9\u6cd5\u3002\u63a5\u53e3\u4e2d\u7684\u5177\u4f53\u65b9\u6cd5\u6709\u4e24\u79cd\uff0cdefault\u65b9\u6cd5\u548cstatic\u65b9\u6cd5\u3002<\/p>\n

@FunctionalInterface\ninterface TestFunctionService\n{\n    void addHttp(String url);\n}<\/code><\/pre>\n
\u90a3\u4e48\u5c31\u53ef\u4ee5\u4f7f\u7528Lambda\u8868\u8fbe\u5f0f\u6765\u8868\u793a\u8be5\u63a5\u53e3\u7684\u4e00\u4e2a\u5b9e\u73b0\u3002<\/p>\n
TestFunctionService testFunctionService = url -> System.out.println("http:" + url);<\/code><\/pre>\n
2.1 FunctionalInterface<\/h4>\n
2.1.1 \u6e90\u7801<\/h5>\n
@Documented\n@Retention(RetentionPolicy.RUNTIME)\n@Target(ElementType.TYPE)\npublic @interface FunctionalInterface {}<\/code><\/pre>\n
2.1.2 \u8bf4\u660e<\/h5>\n
\"\"<\/p>\n
\u4e0a\u56fe\u662fFunctionalInterface\u7684\u6ce8\u89e3\u8bf4\u660e\u3002\u901a\u8fc7\u4e0a\u9762\u7684\u6ce8\u89e3\u8bf4\u660e\uff0c\u53ef\u4ee5\u77e5\u9053FunctionalInterface\u662f\u4e00\u4e2a\u6ce8\u89e3\uff0c\u7528\u6765\u8bf4\u660e\u4e00\u4e2a\u63a5\u53e3\u662f\u51fd\u6570\u5f0f\u63a5\u53e3\u3002 \u51fd\u6570\u5f0f\u63a5\u53e3\u53ea\u6709\u4e00\u4e2a\u62bd\u8c61\u65b9\u6cd5\u3002 \u53ef\u4ee5\u6709\u9ed8\u8ba4\u65b9\u6cd5\uff0c\u56e0\u4e3a\u9ed8\u8ba4\u65b9\u6cd5\u6709\u4e00\u4e2a\u5b9e\u73b0\uff0c\u6240\u4ee5\u4e0d\u662f\u62bd\u8c61\u7684\u3002\u51fd\u6570\u63a5\u53e3\u7684\u5b9e\u4f8b\u53ef\u4ee5\u7528lambda\u8868\u8fbe\u5f0f\u3001\u65b9\u6cd5\u5f15\u7528\u6216\u6784\u9020\u51fd\u6570\u5f15\u7528\u521b\u5efa\u3002<\/p>\n
FunctionalInterface\u4f1a\u6821\u9a8c\u63a5\u53e3\u662f\u5426\u6ee1\u8db3\u51fd\u6570\u5f0f\u63a5\u53e3\uff1a<\/p>\n
    \n
  • \u7c7b\u578b\u5fc5\u987b\u662f\u63a5\u53e3\u7c7b\u578b\uff0c\u4e0d\u80fd\u662f\u6ce8\u91ca\u7c7b\u578b\u3001\u679a\u4e3e\u6216\u7c7b\u3002<\/li>\n
  • \u53ea\u80fd\u6709\u4e00\u4e2a\u62bd\u8c61\u65b9\u6cd5\u3002<\/li>\n
  • \u53ef\u4ee5\u6709\u591a\u4e2a\u9ed8\u8ba4\u65b9\u6cd5\u548c\u9759\u6001\u65b9\u6cd5\u3002<\/li>\n
  • \u53ef\u4ee5\u663e\u793a\u8986\u76d6java.lang.Object\u4e2d\u7684\u62bd\u8c61\u65b9\u6cd5\u3002<\/li>\n<\/ul>\n
    \u7f16\u8bd1\u5668\u4f1a\u5c06\u6ee1\u8db3\u51fd\u6570\u5f0f\u63a5\u53e3\u5b9a\u4e49\u7684\u4efb\u4f55\u63a5\u53e3\u89c6\u4e3a\u51fd\u6570\u5f0f\u63a5\u53e3\uff0c\u800c\u4e0d\u7ba1\u8be5\u63a5\u53e3\u58f0\u660e\u4e2d\u662f\u5426\u4f7f\u7528FunctionalInterface\u6ce8\u89e3\u3002<\/p>\n
    3 Function\u63a5\u53e3\u4e3b\u8981\u5206\u7c7b<\/h3>\n
    Function\u63a5\u53e3\u4e3b\u8981\u5206\u7c7b:<\/p>\n
      \n
    • Function\uff1aFunction\u51fd\u6570\u7684\u8868\u73b0\u5f62\u5f0f\u4e3a\u63a5\u6536\u4e00\u4e2a\u53c2\u6570\uff0c\u5e76\u8fd4\u56de\u4e00\u4e2a\u503c\u3002<\/li>\n
    • Supplier\uff1aSupplier\u7684\u8868\u73b0\u5f62\u5f0f\u4e3a\u4e0d\u63a5\u53d7\u53c2\u6570\u3001\u53ea\u8fd4\u56de\u6570\u636e\u3002<\/li>\n
    • Consumer\uff1aConsumer\u63a5\u6536\u4e00\u4e2a\u53c2\u6570\uff0c\u6ca1\u6709\u8fd4\u56de\u503c\u3002<\/li>\n
    • Runnable\uff1aRunnable\u7684\u8868\u73b0\u5f62\u5f0f\u4e3a\u5373\u6ca1\u6709\u53c2\u6570\u4e5f\u6ca1\u6709\u8fd4\u56de\u503c\u3002<\/li>\n<\/ul>\n
      3.1 Function<\/h4>\n
      Function\u51fd\u6570\u7684\u8868\u73b0\u5f62\u5f0f\u4e3a\u63a5\u6536\u4e00\u4e2a\u53c2\u6570\uff0c\u5e76\u8fd4\u56de\u4e00\u4e2a\u503c\u3002<\/p>\n
      3.1.1 \u6e90\u7801<\/h5>\n
      @FunctionalInterface\npublic interface Function<T, R> {\n    R apply(T t);\n    default <V> Function<V, R> compose(Function<? super V, ? extends T> before) {\n        Objects.requireNonNull(before);\n        return (V v) -> apply(before.apply(v));\n    }\n    default <V> Function<T, V> andThen(Function<? super R, ? extends V> after) {\n        Objects.requireNonNull(after);\n        return (T t) -> after.apply(apply(t));\n    }\n    static <T> Function<T, T> identity() {\n        return t -> t;\n    }\n}<\/code><\/pre>\n
      3.1.2 \u65b9\u6cd5\u8bf4\u660e<\/h5>\n
        \n
      • apply\uff1a\u62bd\u8c61\u65b9\u6cd5\u3002\u5c06\u6b64\u51fd\u6570\u5e94\u7528\u4e8e\u7ed9\u5b9a\u7684\u53c2\u6570\u3002\u53c2\u6570t\u901a\u8fc7\u5177\u4f53\u7684\u5b9e\u73b0\u8fd4\u56deR\u3002<\/li>\n
      • compose\uff1adefault\u65b9\u6cd5\u3002\u8fd4\u56de\u4e00\u4e2a\u590d\u5408\u51fd\u6570\uff0c\u9996\u5148\u6267\u884cfefore\u51fd\u6570\u5e94\u7528\u4e8e\u8f93\u5165\uff0c\u7136\u540e\u5c06\u8be5\u51fd\u6570\u5e94\u7528\u4e8e\u7ed3\u679c\u3002\u5982\u679c\u4efb\u610f\u4e00\u4e2a\u51fd\u6570\u7684\u6c42\u503c\u5f15\u53d1\u5f02\u5e38\uff0c\u5219\u5c06\u5176\u4f20\u9012\u7ed9\u7ec4\u5408\u51fd\u6570\u7684\u8c03\u7528\u8005\u3002<\/li>\n
      • andThen\uff1adefault\u65b9\u6cd5\u3002\u8fd4\u56de\u4e00\u4e2a\u590d\u5408\u51fd\u6570\uff0c\u8be5\u590d\u5408\u51fd\u6570\u9996\u5148\u5bf9\u5176\u5e94\u7528\u6b64\u51fd\u6570\u5b83\u7684\u8f93\u5165\uff0c\u7136\u540e\u5bf9\u7ed3\u679c\u5e94\u7528after\u51fd\u6570\u3002\u5982\u679c\u4efb\u610f\u4e00\u4e2a\u51fd\u6570\u7684\u6c42\u503c\u5f15\u53d1\u5f02\u5e38\uff0c\u5219\u5c06\u5176\u4f20\u9012\u7ed9\u7ec4\u5408\u51fd\u6570\u7684\u8c03\u7528\u8005\u3002<\/li>\n
      • identity\uff1astatic\u65b9\u6cd5\u3002\u8fd4\u56de\u4e00\u4e2a\u59cb\u7ec8\u8fd4\u56de\u5176\u8f93\u5165\u53c2\u6570\u7684\u51fd\u6570\u3002<\/li>\n<\/ul>\n
        3.1.3 \u65b9\u6cd5\u4e3e\u4f8b<\/h5>\n
        1\uff09apply<\/p>\n
        \u6d4b\u8bd5\u4ee3\u7801\uff1a<\/p>\n
        public  String upString(String str){\n    Function<String, String> function1 = s -> s.toUpperCase();\n    return function1.apply(str);\n}\n public static void main(String[] args) {\n     System.out.println(upString("hello!"));\n }<\/code><\/pre>\n
        \u901a\u8fc7apply\u8c03\u7528\u5177\u4f53\u7684\u5b9e\u73b0\u3002\u6267\u884c\u7ed3\u679c\uff1a<\/p>\n
        \"\"<\/p>\n
        2\uff09compose<\/p>\n
        \u6d4b\u8bd5\u4ee3\u7801\uff1a<\/p>\n
        public static void main(String[] args) {\n    Function<String, String> function1 = s -> s.toUpperCase();\n    Function<String, String> function2 = s -> "my name is "+s;\n    String result = function1.compose(function2).apply("zhangSan");\n    System.out.println(result);\n}<\/code><\/pre>\n
        \u6267\u884c\u7ed3\u679c<\/p>\n
        \"\"<\/p>\n
        \u5982\u7ed3\u679c\u6240\u793a\uff1acompose \u5148\u6267\u884cfunction2 \u540e\u6267\u884cfunction1\u3002<\/p>\n
        3\uff09andThen<\/p>\n
        \u6d4b\u8bd5\u4ee3\u7801\uff1a<\/p>\n
        public static void main(String[] args) {\n    Function<String, String> function1 = s -> s.toUpperCase();\n    Function<String, String> function2 = s -> "my name is "+s;\n    String result = function1.andThen(function2).apply("zhangSan");\n    System.out.println(result);\n}<\/code><\/pre>\n
        \u6267\u884c\u7ed3\u679c\uff1a<\/p>\n
        \"\"<\/p>\n
        \u5982\u7ed3\u679c\u6240\u793a\uff1a<\/p>\n
        andThen\u5148\u6267\u884cfunction1 \u540e\u6267\u884cfunction2\u3002<\/p>\n
          \n
        • identity<\/li>\n<\/ul>\n
          \u6d4b\u8bd5\u4ee3\u7801\uff1a<\/p>\n
          public static void main(String[] args) {\n    Stream<String> stream = Stream.of("order", "good", "lab", "warehouse");\n    Map<String, Integer> map = stream.collect(Collectors.toMap(Function.identity(), String::length));\n    System.out.println(map);\n}<\/code><\/pre>\n
          \u6267\u884c\u7ed3\u679c:<\/p>\n
          \"\"<\/p>\n
          3.2 Supplier<\/h4>\n
          Supplier\u7684\u8868\u73b0\u5f62\u5f0f\u4e3a\u4e0d\u63a5\u53d7\u53c2\u6570\u3001\u53ea\u8fd4\u56de\u6570\u636e\u3002<\/p>\n
          3.2.1 \u6e90\u7801<\/h5>\n
          @FunctionalInterface\npublic interface Supplier<T> {\n    \/**\n     * Gets a result.\n     *\n     * @return a result\n     *\/\n    T get();\n}<\/code><\/pre>\n
          3.2.2 \u65b9\u6cd5\u8bf4\u660e<\/h5>\n
          get\uff1a\u62bd\u8c61\u65b9\u6cd5\u3002\u901a\u8fc7\u5b9e\u73b0\u8fd4\u56deT\u3002<\/p>\n
          3.2.3 \u65b9\u6cd5\u4e3e\u4f8b<\/h5>\n
          public class SupplierTest {\n    SupplierTest(){\n        System.out.println(Math.random());\n        System.out.println(this.toString());\n    }\n}\n    public static void main(String[] args) {\n        Supplier<SupplierTest> sup = SupplierTest::new;\n        System.out.println("\u8c03\u7528\u4e00\u6b21");\n        sup.get();\n        System.out.println("\u8c03\u7528\u4e8c\u6b21");\n        sup.get();\n}<\/code><\/pre>\n
          \u6267\u884c\u7ed3\u679c:<\/p>\n
          \"\"<\/p>\n
          \u5982\u7ed3\u679c\u6240\u793a\uff1aSupplier\u5efa\u7acb\u65f6\u5e76\u6ca1\u6709\u521b\u5efa\u65b0\u7c7b\uff0c\u6bcf\u6b21\u8c03\u7528get\u8fd4\u56de\u7684\u503c\u4e0d\u662f\u540c\u4e00\u4e2a\u3002<\/p>\n
          3.3 Consumer<\/h4>\n
          Consumer\u63a5\u6536\u4e00\u4e2a\u53c2\u6570\uff0c\u6ca1\u6709\u8fd4\u56de\u503c\u3002<\/p>\n
          3.3.1 \u6e90\u7801<\/h5>\n
          @FunctionalInterface\npublic interface Consumer<T> {\n    void accept(T t);\n    default Consumer<T> andThen(Consumer<? super T> after) {\n        Objects.requireNonNull(after);\n        return (T t) -> { accept(t); after.accept(t); };\n    }\n}<\/code><\/pre>\n
          3.3.2 \u65b9\u6cd5\u8bf4\u660e<\/h5>\n