MainActivity.java file

 package com.example.courtcounter;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    int scoreTeamA = 0;
    int scoreTeamB = 0;

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

    public void display3(View view) {
        scoreTeamA = scoreTeamA + 3;
        displayForTeamA(scoreTeamA);
    }

    public void display2(View view) {
        scoreTeamA = scoreTeamA + 2;
        displayForTeamA(scoreTeamA);
    }

    public void display1(View view) {
        scoreTeamA = scoreTeamA + 1;
        displayForTeamA(scoreTeamA);
    }

    public void displayB3(View view) {
        scoreTeamB = scoreTeamB + 3;
        displayForTeamB(scoreTeamB);
    }

    public void displayB2(View view) {
        scoreTeamB = scoreTeamB + 2;
        displayForTeamB(scoreTeamB);
    }

    public void displayB1(View view) {
        scoreTeamB = scoreTeamB + 1;
        displayForTeamB(scoreTeamB);
    }

    public void reset(View view){
        scoreTeamA = 0;
        scoreTeamB = 0;
        displayForTeamA(scoreTeamA);
        displayForTeamB(scoreTeamB);
    }
    /**
     * Displays the given score for Team A.
     */
    public void displayForTeamA(int score) {
        TextView scoreView = (TextView) findViewById(R.id.team_a_score);
        scoreView.setText(String.valueOf(score));
    }

    public void displayForTeamB(int score) {
        TextView scoreView = (TextView) findViewById(R.id.team_b_score);
        scoreView.setText(String.valueOf(score));
    }
}