Android Activity Life Cycle

package com.example.mycalculator;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    EditText num1, num2;
    TextView result;
    Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //1
        setContentView(R.layout.activity_main);
        Log.d("ON_CREATE", "called");
    }

    @Override
    protected void onStart() {
        super.onStart();
        //2
        Log.d("ON_START", "called");
    }

    @Override
    protected void onResume() {
        super.onResume();
       //3
        Log.d("ON_RESUME", "called");
    }

    @Override
    protected void onPause() {
        super.onPause();
        //4 when another activity is visible
        Log.d("ON_PAUSE", "called");
    }


    @Override
    protected void onStop() {
        super.onStop();
        //5 when activity is no longer visible
        Log.d("ON_STOP", "called");
    }

    @Override
    protected void onRestart() {
        super.onRestart();
            //6 this comes after onStop method
        Log.d("ON_RESTART", "called");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
            // 7 before when application being killed.
        Log.d("ON_DESTROY", "called");
    }
}