Number Guessing Game in JAVA

Question

I am writing random number guessing game and cant figure out as to why my method UpdateUI is lit up red?

package com.example.guessmynumber;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import java.util.Random;

public class MainActivity extends AppCompatActivity {

static final int CORRECT = 0;
static final int LOW = 1;
static final int HIGH = 2;
static final int RESET = 3;
static final int MAX_NUMBER = 101;

TextView userNumber, textPrevious;
EditText userInput;
Button submitButton;
int target;
Random generator;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

userNumber = findViewById(R.id.user_number);
userInput = findViewById(R.id.user_input);
submitButton = findViewById(R.id.submit_button);
textPrevious = findViewById(R.id.text_previous);
generator = new Random();

submitButton.setOnClickListener(new View.OnClickListener( ) {
@Override
public void onClick(View v) {
if(submitButton.getText() == getString(R.string.app_name)) {
int guess = Integer.parseInt(userInput.getText( ).toString( ));
userInput.setText(Integer.toString(guess));

UpdateUI(checkGuess(guess));
}else{
target = generator.nextInt(MAX_NUMBER);

UpdateUI(RESET);

}
}

});

}

@Override
protected void onStart(){
super.onStart();
int target = generator.nextInt(MAX_NUMBER);

}

private int checkGuess(int guess){
if (guess == target) {

Answer 1

Where’s the UpdateUI function? I cant find it

Answer 2

the UpdateUi() is not defined bro, that is why its red

Answer 3

what do u mean

Answer 4

Hiw would I go about doing that? Is it in styles?