Google suggests
Apache Commons Collections By the way, the package naming convention is to use a domain name for the first two packages, putting the top-level first. It is a simple way to provide a large name space and to provide hints as to where one could find a file. If, from your example, you pointed your browser at apache.org (the first two packages) and looked for a link to commons, then a link for collections, you'd be exactly where I linked above.
[ March 14, 2008: Message edited by: Joe Ess ]