Android, Java, onSaveInstanceState.

PersistentData.java

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    /*
     * If savedInstanceState is not null, that means our Activity is not being started for the
     * first time. Even if the savedInstanceState is not null, it is smart to check if the
     * bundle contains the key we are looking for.
     */
    if (savedInstanceState != null) {
        if (savedInstanceState.containsKey(BUNDLE_KEY)) {
            String textRestored = savedInstanceState.getString(BUNDLE_KEY);
        }
    }
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putString(BUNDLE_KEY, textToSave);
}