Case classes can be seen as plain and immutable data-holding objects that should exclusively depend on their constructor arguments.
This functional concept allows us to
- use a compact initialization syntax (
Node(1, Leaf(2), None)))
- decompose them using pattern matching
- have equality comparisons implicitly defined
In combination with inheritance, case classes are used to mimic algebraic datatypes.
If an object performs stateful computations on the inside or exhibits other kinds of complex behaviour, it should be an ordinary class.