code: public double readDouble(double defaultValue, String attribute)
      {
          return Double.parseDouble(getValue(String.valueOf(defaultValue), attribute));
      }
docs: Read a double.
  
  @param defaultValue The value returned if attribute not found.
  @param attribute The double name (must not be <code>null</code>).
  @return The double value.
  @throws LionEngineException If invalid argument.