How to use setOnClickListener to the buttons in android using java

Question

Unable to start activity ComponentInfo{com.example.sulejo9.gato/com.example.sulejo9.gato.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

I am getting the error above, what I dont understand is how to implemment my set onclicklistener, for all my buttons in [x][y]

I dont seem to see why buttonreset is my variable, when im calling it in this line

private Button[][] buttons = new Button[3][3];


public class MainActivity extends AppCompatActivity  implements View.OnClickListener{


    private Button[][] buttons = new Button[3][3];

    private TextView textViewPlayer;
    private TextView textViewNpc;


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

        //Referencias a los textview
        textViewPlayer = findViewById(R.id.text_view_Player);
        textViewNpc = findViewById(R.id.text_view_NPC);


        for (int x = 0; x < 3; x++) {
            for (int y = 0; y < 3; y++) {
                String buttonID = "button_" + x + y;
                int resID = getResources().getIdentifier(buttonID, "id", getPackageName()); //5:08
                buttons[x][y] = findViewById(resID);
                buttons[x][y].setOnClickListener(this);
            }
        }
        Button buttonReset = findViewById(R.id.button_reset);
        buttonReset.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });
    }