NPE at sun.nio.ch.Util.free(Util.java:199)

We are using a third party application which uses sun.nio package. We are facing following error very frequently,

java.lang.NullPointerException
    at sun.nio.ch.Util.free(Util.java:199)
    at sun.nio.ch.Util.offerFirstTemporaryDirectBuffer(Util.java:176)
    at sun.nio.ch.IOUtil.write(IOUtil.java:50)
    at sun.nio.ch.SocketChannelImpl.write(SocketChannelImpl.java:334)

This d开发者_开发知识库oes not stop until the servers are restarted. Overall memory consumption remains at 30%.

I tried searching for this and sun.nio package but could not get any pointers to it. What I am looking for followings

1. Any articles, documentations regarding sun.nio package
2. Source code would be a great help.
3. If you guys have any hint of what "might be" happening in this case, please share the same.

Here is decompiled source of Util available:

http://www.text-upload.com/read.php?id=141860&c=8070720