reflect vs MethodHandles

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.reflect.Method;

/**
 * @author paul
 * @description
 * @date 2018/11/27
 */
public class RunMethod {
    public static void reflection() throws Exception {
        String methodName = "substring";
        Method method = String.class.getDeclaredMethod(methodName, new Class[]{int.class, int.class});
        String str = (String) method.invoke("Hello World", new Object[]{1, 3});
        System.out.println(str);
    }

    public static void invokeExact() throws Throwable {
        MethodHandles.Lookup lookup = MethodHandles.lookup();
        //(II)Ljava/lang/String;
        MethodType type = MethodType.methodType(String.class, int.class, int.class);
        MethodHandle mh = lookup.findVirtual(String.class, "substring", type);
        String o = (String) mh.invokeExact("Hello World", 1, 3);
        //这里的(String必须填写，否则找不到对应的方法)
        System.out.println(o);
    }

    public static void main(String[] args) throws Throwable {
        reflection();
        invokeExact();
    }
}