code: public void setPrototype(final File prototype) {
      if (isReference()) {
        throw tooManyAttributes();
      }
      if (prototype == null) {
        throw new NullPointerException("prototype");
      }
      this.prototype = prototype;
    }
docs: Sets file to precompile.
  
  Should be a source file that includes only one unguarded header file.
  Default value is "stdafx.cpp".
  
  @param prototype
  file path for prototype source file