Click Event handing using OnClickListener Listener Interface

MainActivity.java

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private ConstraintLayout constraintLayout;
    private Button button1;
    private Button button2;

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

        constraintLayout = findViewById(R.id.c);
        button1 = findViewById(R.id.button1);
        button1.setOnClickListener(this);
        button2 = findViewById(R.id.button2);
        button2.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        int id = view.getId();
        if (id==R.id.button1){
            constraintLayout.setBackgroundColor(Color.GREEN);
        }else if (id==R.id.button2){
            constraintLayout.setBackgroundColor(Color.BLUE);
        }
    }
}