java.awt.geom.Area class overrides Object.equals but not Object.hashCode. This violates the restriction that:

a.equals(b) ==> a.hashCode()==b.hashCode()

If our customers use objects of any of these classes as keys in Hashtables or
HashMaps, or elements in HashSets, the basic invariants of the collections will
be corrupted, leading to erratic behavior.

We have fixed this problem for awt (see bug 4157612)