I am making most of my basic types in my app, immutable. But should the collections be immutable too? To me, this seems like a huge overhead unless I am missing something.
I am talking about collections to hold Point3 values, etc which can be added as it goes at different times. So if there are 1M values in a collection, and you needed to delete 1 of them, you would have to create the same collection all over again, right?
I agree with Eric's comments about choosing the right tool for the problem. Immutability adds value when your goals include providing clear identity semantics, or making your implementation easier to work with in a parallel computing environment. Immutability can also help improve performance by allowing optimizations such as caching or transparent proxying.
On the flip-side, immutability can also incur a performance cost - particularly when you use the "copy-on-write" pattern to model "changes".
You have to decide why you want your entities/collections to be immutable - and that will help drive your decision of whether to do so or not.