RFR: 8059169 [Findbugs]Classes under package com.sun.tools.internal.xjc may expose internal representation by storing an externally mutable object

[Eric Guo]

Hi all,

Could you please help me to review my code change about issue 
https://bugs.openjdk.java.net/browse/JDK-8059169 ?

webrev: http://cr.openjdk.java.net/~fyuan/eguo/8059169/webrev.00/ . 
These change are only for JDK 9.

Best regards,
Eric