I have an object that may contain several other objects (sub-object) and will compress those sub-objects.

My question is generally what is a good way to compare two objects, as described above, if they are equal (e.g. through equals() function)?

Intuitively there are two ways I can think of:

1. Compare each compressed bit

The disadvantage I think is it's not efficient if the object is very big. For instance, when it holds several gigabytes data, it may took too long for just comparing each bit.

2. Hash the sub-object before compressing it, and then compare all hashed values.

This problem is I am not very sure if hashing is a good way to compare objects. And if collision may be the problem?

Is there other better way to achieve it?

I appreciate any suggestions.

Thank you!