jhat can show root set references (i.e., set of all paths by which a specific object is alive). While showing rootset references, user can filter "exclude weak refs". In this mode, paths the contain one or more java.lang.ref.Reference (or any subclass) in it will be filtered. This helps in OOM analysis -- user may want to skip weak/soft paths. But, this facility does not work as expected. For eg. paths with WeakReference (or it's subclass) objects are shown in "exclude weak refs" mode.