How to handle HTTP PUT request to update user details in Spring Boot

import java.util.HashMap;
import java.util.Map;
import javax.validation.Valid;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.behindjava.tutorial.model.UserModel;

@RestController
@RequestMapping("/users")
public class UserController {

	HashMap<String, UserModel> user;

	@PostMapping(produces = { MediaType.APPLICATION_JSON_VALUE, MediaType.APPLICATION_XML_VALUE }, consumes = {
			MediaType.APPLICATION_JSON_VALUE, MediaType.APPLICATION_XML_VALUE })
	public ResponseEntity<UserModel> createUser(@Valid @RequestBody UserModel us) {

		UserModel um = new UserModel();
		um.setEmail(us.getEmail());
		um.setFirstname(us.getFirstname());
		um.setLastname(us.getLastname());
		um.setUserId(us.getUserId());

		if (user == null)
			user = new HashMap<>();
		user.put(us.getUserId(), um);

		return new ResponseEntity<UserModel>(um, HttpStatus.CREATED);
	}

	@GetMapping(path = "/{userId}", produces = { MediaType.APPLICATION_XML_VALUE, MediaType.APPLICATION_JSON_VALUE })
	public ResponseEntity<UserModel> getUser(@PathVariable String userId) {

		if (user.containsKey(userId)) {
			return new ResponseEntity<UserModel>(user.get(userId), HttpStatus.CREATED);
		} else {
			return new ResponseEntity<UserModel>(HttpStatus.NO_CONTENT);
		}

	}

	@PutMapping(path = "/{userId}", produces = { MediaType.APPLICATION_JSON_VALUE,
			MediaType.APPLICATION_XML_VALUE }, consumes = { MediaType.APPLICATION_JSON_VALUE,
					MediaType.APPLICATION_XML_VALUE })
	public UserModel updateUser(@Valid @PathVariable String userId, @RequestBody UserModel us) {
		UserModel usr = user.get(userId);
		usr.setFirstname(us.getFirstname());
		usr.setLastname(us.getLastname());
		usr.setEmail(us.getEmail());
		user.put(userId, usr);
		return usr;
	}
}