Empirical data on the effects of immutability?

Question

In class today, my professor was discussing how to structure a class. The course primarily uses Java and I have more Java experience than the teacher (he comes from a C++ b

Answer 1

I would point to Item 15 in Effective Java. The value of immutability is in the design (and it isn't always appropriate - it is just a good first approximation) and design preferences are rarely argued from a statistical point of view, but we have seen mutable objects (Calendar, Date) that have gone really bad, and serious replacements (JodaTime, JSR-310) have opted for immutability.