code: public String getString(String key) throws MissingResourceException {
          // Error Checking Trace.  Ensure that we got a valid key
          if (key == null) {
              if (tc.isEventEnabled()) {
  
                  // DGH20040823: Begin fix for defect 218797 - Source provided by Tom Musta
                  // String msg = messages.getString("NLS.nullKey",
                  //                                 "Null lookup key passed to NLS");
                  String msg = getMessages().getString("NLS.nullKey",
                                                       "Null lookup key passed to NLS");
                  // DGH20040823: End fix for defect 218797 - Source provided by Tom Musta
                  Tr.warning(tc, msg);
              }
              return null;
          }
          // Error Checking Trace.  Ensure that we got a valid bundle.
          if (bundle == null) {
              if (tc.isEventEnabled()) {
                  // DGH20040823: Begin fix for defect 218797 - Source provided by Tom Musta
                  // String msg = messages.getString("NLS.noBundles",
                  //                                 "Encountered an internal error. No valid bundles.");
                  String msg = getMessages().getString("NLS.noBundles",
                                                       "Encountered an internal error. No valid bundles.");
                  // DGH20040823: End fix for defect 218797 - Source provided by Tom Musta
                  Tr.warning(tc, msg);
              }
              throw new MissingResourceException(bundleName, bundleName, key);
          }
          // Return Code.
          String rtn = null;
          // Get the resource (string).
          rtn = bundle.getString(key);
          return rtn;
      }
docs: Overrides ResourceBundle.getString. Adds some error checking to ensure that
  we got a non-null key and resource bundle.
  
  @param key Name portion of "name=value" pair.
  @return rtn The resource string.