java android

package com.example.bau.counter;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private Button countButton, resetButton;
    private TextView mTextViewCounter;
    private RadioGroup mRadioGroup;
    private RadioButton upRadio, downRadio;
    private int counter = 0;

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

        countButton = (Button) findViewById(R.id.countButton);
        resetButton = (Button) findViewById(R.id.resetButton);
        mTextViewCounter = (TextView) findViewById(R.id.counterTab);
        mRadioGroup = (RadioGroup) findViewById(R.id.radioGroup);
        upRadio = (RadioButton) findViewById(R.id.countUpRadio);
        downRadio = (RadioButton) findViewById(R.id.countDownRadio);

        upRadio.toggle();

        countButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int checked = mRadioGroup.getCheckedRadioButtonId();

                if (checked == upRadio.getId()) {
                    counter++;
                    Toast.makeText(MainActivity.this, "Incrementing the counter", Toast.LENGTH_SHORT).show();
                }
                else if (checked == downRadio.getId()) {
                    counter--;
                    Toast.makeText(MainActivity.this, "Decrementing the counter", Toast.LENGTH_SHORT).show();
                }

                mTextViewCounter.setText(counter + "");
            }
        });

        resetButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                counter = 0;
                mTextViewCounter.setText(counter + "");
            }
        });

    }
}