Chapter 8

Question 1

What is inheritance in Java?

Answer 1

Inheritance allows one class (subclass) to inherit fields and methods from another class (superclass), enabling code reuse and hierarchy modeling.

Question 2

How is inheritance implemented in Java?

Answer 2

Using the extends keyword.

```java
class Subclass extends Superclass { }
~~~

Question 3

What does the super keyword do?

Answer 3

It refers to the parent class. Can be used to call:

• A superclass method: super.methodName()
• A superclass constructor: super(args) (must be the first line in constructor)

Question 4

What does super() do specifically in a constructor?

Answer 4

Calls the constructor of the parent class. Java inserts it implicitly only if the parent has a no-argument constructor.

Question 5

What is method overriding?

Answer 5

A subclass provides a specific implementation of a method already defined in the superclass. The method must have the same name, return type, and parameters.

Question 6

How do you indicate a method is overridden?

Answer 6

Use the @Override annotation above the method.

Question 7

What is the difference between method overloading and overriding?

Answer 7

• Overriding: Same method name & parameters in parent-child relationship.
• Overloading: Same method name, different parameters in the same class.

Question 8

What is polymorphism in Java?

Answer 8

The ability of a subclass object to be treated as an object of its superclass.

Question 9

What members are inherited by a subclass?

Answer 9

All non-private fields and methods. private members are not inherited directly.

Question 10

Can a class extend more than one class?

Answer 10

No. Java supports single inheritance only.

Question 11

What is the final keyword used for in inheritance?

Answer 11

• final class: cannot be subclassed.
• final method: cannot be overridden.

Question 12

What’s the difference between an abstract class and an interface?

Answer 12

• Abstract class: Can have fields, constructors, and some implementation.
• Interface: Purely abstract (though Java 8+ allows default methods). Supports multiple inheritance.

Question 13

When should you use abstract classes vs. interfaces?

Answer 13

• Use abstract class for “is-a” relationships with shared implementation.
• Use interface for unrelated types needing common behavior.

Question 14

What’s the difference between inheritance and composition?

Answer 14

• Inheritance: “is-a” relationship (e.g., Dog is-an Animal).
• Composition: “has-a” relationship (e.g., Car has-an Engine).

Question 15

What are the benefits of using inheritance?

Answer 15

1. Code reuse
2. Logical hierarchy
3. Polymorphism
4. Centralized maintenance
5. Extensibility

Question 16

What is constructor chaining in inheritance?

Answer 16

When a subclass constructor calls a superclass constructor using super().

Question 17

Can a subclass override a private or static method?

Answer 17

• private: Cannot be accessed or overridden.
• static: Can be redefined but not truly overridden (called shadowing).