code: private void checkMemoryManagementOption(MemoryManagementOption option) {
      if (memoryManagementOption != null && memoryManagementOption != option) {
        usage("Multiple memory management options cannot be set.");
      }
      setMemoryManagementOption(option);
    }
docs: Check that the memory management option wasn't previously set to a
  different value.  If okay, then set the option.