Mutable Variable, Mutable Function
An immutable data type is one for which an instance cannot change in any observable way after instantiation.
Example:
- Mutable: ArrayDeque
- Immutable: Integer, String
The final keyword will help the compiler ensure immutability.(But not necessary to have final to be immutable, maybe just there is no code, no method, etc. to change this value)
(Month, day, year is final and contrived is private and no method to changes in outside nor inside)
Warning: Declaring a reference as final does not make object immutable.
Example: public final ArrayDeque<String> d = new ArrayDeque<>()
The d variable can never change, but the referenced deque can!
Just like pointer constant in C: int * const p