靜態分派與動態分派

靜態分派

自動轉型按照 char > int > long > float > double

如下面案例所示：

public class Test {
    public static void sayHello(char arg) {
        System.out.println("hello char");
    }

    public static void sayHello(int arg) {
        System.out.println("hello int");
    }

    public static
 
 void sayHello(long arg) {
        System.out.println("hello long");
    }

    public static void sayHello(Character arg) {
        System.out.println("hello Character");
    }

    public static void main(String[] args) {
        sayHello('a');
    }
}

動態分派

如下面案例所示：

public class MethodHandleTest
 
 {
    public static class ClassA{
        public  void println(String s){
            System.out.println(s + ".ClassA");
        }
    }

    public static void main(String[] arge) {
        Object obj = System.currentTimeMillis() % 2 == 0 ? System.out : new ClassA();
//
        try {
            getPlantMH(obj).invokeExact("hello"
 
);
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (Throwable throwable) {
            throwable.printStackTrace();
        }


    }

    private static MethodHandle getPlantMH(Object reveiver) throws NoSuchMethodException, IllegalAccessException {
        MethodType mt = MethodType.methodType(void.class, String.class);

        return lookup().findVirtual(reveiver.getClass(), "println", mt).bindTo(reveiver);
    }
}