code: protected void demo() throws Throwable {
  	    MethodHandles.Lookup lookup = MethodHandles.lookup();
  	    MethodType type = MethodType.methodType(String.class, int.class, int.class);
  	    MethodHandle mh = lookup.findVirtual(String.class, "substring", type);
  	    String str = (String) mh.invokeExact("Hello World", 1, 3);
  	    System.out.println(str);
  	}
docs: JDK 7及以上的方法句柄方式调用
  @throws Throwable