How to setup a User LogIn / Logout / Signup

Parse User.java

package com.parse.starter;

import android.content.Intent;
import android.database.Cursor;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ImageView;

import com.parse.FindCallback;
import com.parse.GetCallback;
import com.parse.LogInCallback;
import com.parse.Parse;
import com.parse.ParseAnalytics;
import com.parse.ParseException;
import com.parse.ParseObject;
import com.parse.ParseQuery;
import com.parse.ParseUser;
import com.parse.SaveCallback;
import com.parse.SignUpCallback;

import java.util.List;


public class MainActivity extends AppCompatActivity {

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


      
      ParseUser user = new ParseUser();   //create a new user 
      user.setUsername("robpercival"); //set user "username"
      user.setPassword("myPass"); // set user "password"

      user.signUpInBackground(new SignUpCallback() {
          @Override
          public void done(ParseException e) {   // feedback if signning up process gone OK

              if (e == null) {

                  Log.i("signUp", "Successful");

              } else {

                  Log.i("signUp", "Failed");
                  e.printStackTrace();
              }


          }
      });


      ParseUser.logInInBackground("robpercival", "myPass123", new LogInCallback() {   // log in a user with log in parameters 
          @Override
          public void done(ParseUser user, ParseException e) {   //Feedback if log in gone OK

              if (user != null) {

                  Log.i("logIn", "Successful");

              } else {

                  Log.i("logIn", "Unsuccessful");
                  e.printStackTrace();

              }

          }
      });

        

      ParseUser.logOut();    //log user out

      if (ParseUser.getCurrentUser() != null) {  // check if user still logged in.. Remember him and keep him logging

          Log.i("currentUser", "User logged in");

      } else {

          Log.i("currentUser", "Not logged in");

      }

    ParseAnalytics.trackAppOpenedInBackground(getIntent());


  }

  @Override
  public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
  }

  @Override
  public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
      return true;
    }

    return super.onOptionsItemSelected(item);
  }
}

Read me.txt

- in Starter application. java file the following line must be commented before writting any code at Main_Activity:
 
 ParseUser.enableAutomaticUser();