Convert java object to get the string is garbled

I try to use ‘Invoke Java Method’ and ‘Convert Java Object’ to get a return value and convert to String type, but the value is garbled like that:


I guess that the string variable may contain chinese, if the return value which just contains number and english letter will be ok.
But I try to convert from unicode or gb2312 to UTF-8 but is not useful.
How should I do ?
I am waitting.