code: private void importFromProperties(final URL _url,
                                        final String _language)
      {
          try {
              final InputStream propInFile = _url.openStream();
              final Properties props = new Properties();
              props.load(propInFile);
              final Iterator<Entry<Object, Object>> iter = props.entrySet().iterator();
  
              while (iter.hasNext()) {
                  final Entry<Object, Object> element = iter.next();
                  Instance propInstance = getExistingKey(element.getKey().toString());
                  if (propInstance == null || !propInstance.isValid()) {
                      propInstance = insertNewProp(element.getKey().toString(), element.getValue().toString());
                  }
  
                  final Instance localInstance = getExistingLocale(propInstance.getId(), _language);
                  if (localInstance == null || !localInstance.isValid()) {
                      insertNewLocal(propInstance.getId(), element.getValue().toString(), _language);
                  } else {
                      updateLocale(localInstance, element.getValue().toString());
                  }
              }
  
          } catch (final IOException e) {
              DBPropertiesUpdate.LOG.error("ImportFromProperties() - I/O failed.", e);
          }
      }
docs: Import Properties from a Properties-File as language-specific value, if
  the key is not existing, a new default(=value) will also be created. If
  the language is not existing it will be created also.
  
  @param _url Complete Path/Name of the File to import
  @param _language Language to use for the Import