title: Why does this Android FileOutputStream throw a NullPointerException?
body: <p>There does not seem to be any Android manifest permission that needs to be set for file io.</p>
  
  <pre><code>public class Device extends Activity {
      private static final Configuration config = new Configuration();
      ...
      private boolean applyMenuChoice(MenuItem item) {
          switch (item.getItemId()) {
          ...
          case R.id.menuSave:
              ...
              configuration.modify(name, to, from, user);
              configuration.write();
              ...
  
  public class Configuration extends Activity {
      private final static String CONFIG = "config.txt";
      private static StringBuilder config = new StringBuilder();
      ...
      public void write() {
          try {
              FileOutputStream fos = openFileOutput(CONFIG, Context.MODE_PRIVATE);
              fos.write(config.toString().getBytes());
              ...
  </code></pre>