Core Java 5: Static vs non-static & final keyword

Question 1

Static

Answer 1

belongs to class definition rather than to a specific instance.

Question 2

Where is static useful?

Answer 2

• Constants (public final static)
• Utility methods: methods which take action on given data type & do not require any internal state

Question 3

Why does static break encapsulation?

Answer 3

• Static attributes can be manipulated without having to use instance
• Can change the state an object depends on without talking to class directly

Question 4

final (classes)

Answer 4

if a class is marked as final, it can’t be extended/inherited from.

Question 5

final (methods)

Answer 5

if a method is marked as final, it can’t be overridden.

Question 6

final (attributes)

Answer 6

if an attribute is marked as final, it can’t be modified; often used for constants, such as pi.