Immutable is Good

Make a class immutable when you can (and as immutable as possible when you can’t).

Be careful: Getters must not return a mutable reference to an internal state.

You should not need to provide a copy-constructor on an immutable class. (Don’t copy; just share.)

Don’t provide an initialize method; constructors or factory methods should fully initialize an object.

Don’t provide a reset method for reusing an object; just create a new object.