Accessors, Mutators and Immutable Classes

• Accessor: does not change the state of the implicit parameter

  double balance = account.getBalance();

• Mutator: modifies the object on which it is invoked

  account.deposit(1000);

• Immutable class: has no mutator methods (e.g., String)

  String name = "John Q. Public";
  String uppercased = name.toUpperCase(); // name is not changed

• It is safe to give out references to objects of immutable classes; no code can modify the object at an unexpected time