Use cases for IdentityHashMap

Solution 1:

Whenever you want your keys not to be compared by equals but by == you would use an IdentityHashMap. This can be very useful if you're doing a lot of reference-handling but it's limited to very special cases only.

Solution 2:

The documentations says:

A typical use of this class is topology-preserving object graph transformations, such as serialization or deep-copying. To perform such a transformation, a program must maintain a "node table" that keeps track of all the object references that have already been processed. The node table must not equate distinct objects even if they happen to be equal. Another typical use of this class is to maintain proxy objects. For example, a debugging facility might wish to maintain a proxy object for each object in the program being debugged.