private SharedPreferences sharedPreferences;
private SharedPreferences.Editor editorSharedPreferences;
private String KEY="KEY";

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO

    sharedPreferences = getSharedPreferences(KEY, Context.MODE_PRIVATE);

    editorSharedPreferences = sharedPreferences.edit();
}

editorSharedPreferences.putString(KEY,"TEXT");

editorSharedPreferences.apply();

if (sharedPreferences.contains(KEY)) {
    String text = sharedPreferences.getString(KEY, "");
    // TODO
}

editorSharedPreferences.remove(KEY);
editorSharedPreferences.commit();