code: public String key(String keyName, boolean allowNull) {
  
          try {
              if (m_dictionary != null) {
                  return m_dictionary.get(keyName);
              }
          } catch (@SuppressWarnings("unused") MissingResourceException e) {
              // not found, return warning
              if (allowNull) {
                  return null;
              }
          }
          return formatUnknownKey(keyName);
      }
docs: Returns the localized resource string for a given message key.<p>
  
  If the key was not found in the bundle, the return value
  depends on the setting of the allowNull parameter. If set to false,
  the return value is always a String in the format
  <code>"??? " + keyName + " ???"</code>.
  If set to true, null is returned if the key is not found.
  This will also be returned
  if the bundle was not properly initialized first.
  
  @param keyName the key for the desired string
  @param allowNull if true, 'null' is an allowed return value
  
  @return the resource string for the given key