Unable to get this question

import android.view.View;
import android.os.Bundle;

public class MainActivity extends Activity {

  public CheckBox mCheckBox;
  private static final String PREFS_FILE = "PREFS_FILE.preferences";
  private static final String KEY_CHECKBOX = "KEY_CHECKBOX";
  private SharedPreferences mSharedPreferences;
  private SharedPreferences.Editor mEditor;

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

    mCheckBox = (CheckBox) findViewById(R.id.checkBox);
    mSharedPreferences = getSharedPreferences(PREFS_FILE,Context.MODE_PRIVATE);
    mEditor = mSharedPreferences.edit();

       Boolean checkBoxBoolean = mSharedPreferences.getBoolean(KEY_CHECKBOX,"");

    mCheckBox.setChecked(checkBoxBoolean);
  }

   @Override
  protected void onPause() 
  {
    super.onPause();
    mEditor.putBoolean(KEY_CHECKBOX,mCheckBox.isChecked());
    mEditor.apply();
  }

}