java spring mvc @ResponseBody @Controller  = @RestController

package com.example.demo.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

//@ResponseBody
//@Controller
@RestController

public class helloController {

@RequestMapping("/tt")
public String hello()
{
return "hello world!";
}
}