how to iterate to a previous node with a treemap

I have am using a treemap with the comparable interface. an iterator can be used to go to the 'next' node. How do i go to the 'previous' node?
[154 byte] By [gramberto] at [2007-9-30 21:08:43]
# 1
[url http://forum.java.sun.com/thread.jsp?forum=31&thread=567262]Crosspost[/url]
jverd at 2007-7-7 2:41:58 > top of Java-index,Core,Core APIs...