After wondering for the n-th time about what would be the difference (if any) in toString() representations of a TreeMap and a Vector, I've decided to make a simple catalog for future reference.
Here it is: Java standard classes toString representation catalog [1].
It currently includes only JCF classes.
Links:
[1] http://docs.google.com/View?id=df5k88n3_159dn5nm6fp