code: public String getRequired(String key) {
  		addToDefaults(key, null);
  		String value = get(key);
  		if (value == null) {
  			throw new RuntimeException("No data for required key '" + key + "'");
  		}
  		return value;
  	}
docs: Returns the String value for the given key.
  If the key does not exist it will throw a {@link RuntimeException}.