What is the advantage of immutability

The advantage of immutability comes with concurrency. It is difficult to maintain correctness in mutable objects, as multiple threads could be trying to change the state of the same object, leading to some threads seeing a different state of the same object, depending on the timing of the reads and writes to the said object.

By having an immutable object, one can ensure that all threads that are looking at the object will be seeing the same state, as the state of an immutable object will not change.