What is the difference between final and immutability?
final means that you can’t change the object’s reference to point to another reference or another object, but you can still mutate its state (using setter methods e.g). Whereas immutable means that the object’s actual value can’t be changed, but you can change its reference to another one.
What is the difference between a final class and a final method?
You use the final keyword in a method declaration to indicate that the method cannot be overridden by subclasses. The Object class does this—a number of its methods are final . Note that you can also declare an entire class final. A class that is declared final cannot be subclassed.
Is a final class immutable?
final class can’t be extended by other classes. If a class extend the class you want to make as immutable, it may change the state of the class due to inheritance principles. If you do not make it final I can extend it and make it non mutable.
Why do we use Immutable classes in Java?
Declaring immutable class final saves programmer from the need to repeat declaring final in each and every method declaration, over and over and over again. In classes like java.lang.String, having over 60 methods, this is substantial save, as well as important guarantee that necessary modifier won’t be omitted by mistake.
Do You mark an immutable class as final?
Don’t mark the entire class final. There are valid reasons for allowing an immutable class to be extended as stated in some of the other answers so marking the class as final is not always a good idea. It’s better to mark your properties private and final and if you want to protect the “contract” mark your getters as final.
Why are immutable objects important in object oriented programming?
As such, immutable objects can help enforce good object-oriented programming practices. If you were to take all of an object’s instance variables and write down their values on paper, that would be the state of that object at that given moment. The state of the program is the state of all its objects at a given moment.
How is immutability defined in Objective-C and cocoa?
For instance, Objective-C and Cocoa define both an NSString class (immutable) and an NSMutableString class. If an object is immutable, it can’t be changed after it is created (basically read-only). You could think of it as “only the constructor can change the object”.