If you're just going to find the max, there's no need to sort. Just iterate over the list, keeping track of the largest so far.
If you do need to actually have the list sorted, then look at Collections.sort, or put the values into a SortedSet.
http://java.sun.com/docs/books/tutorial/collections/
[url=http://www.onjava.com/lpt/a/3286]Making Java Objects Comparable[/url]
http://java.sun.com/docs/books/tutorial/collections/interfaces/order.html
http://www.javaworld.com/javaworld/jw-12-2002/jw-1227-sort.html