Got stuck on challenge 4 of 4 Android Activity Lifecycle

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

public class MainActivity extends Activity {

  private static final String PREFS_FILE = "com.packagename.preferences";
  private static final String KEY_CHECKBOX = "KEY_CHECKBOX";

    private SharedPreferences.Editor mEditor;
    private SharedPreferences mSharedPreferences;

  public CheckBox mCheckBox;

  @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 check = SharedPreferences.getBoolean(KEY_CHECKBOX,false);
    mCheckBox.setChecked(check);


  }

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

}