code: public void writeClass(String className)
      throws IOException
    {
      ConstantPool pool =  _javaClass.getConstantPool();
      ClassConstant classConst = pool.getClass(className);
  
      if (classConst != null)
        writeShort(classConst.getIndex());
      else
        writeShort(0);
    }
docs: Writes a class constant.