Main uses of IdentityHashMap are:

1. Topology Preservation: The typical use of

IdentityHashMap class is topology-preserving object

graph transformations, such as serialization or deepcopying. In such a scenario, a program must maintain a

"node table" to keep track of all the object references that

have already been processed.

2. The node table should not considered distinct objects as

equal even if they happen to be equal.

3. Proxy objects: Another use of this class is to maintain

proxy objects. A debugging program has to maintain a

proxy object for each object in the program being

debugged.

https://www.geeksforgeeks.org/identityhashmap-class-java/