Unit 2 Inheritance in Java

What are the four types of inheritance in Java?

• Single and Double Inheritance

• Circular Inheritance

• Static Inheritance

• Single Inheritance, Multilevel Inheritance, Hierarchical Inheritance, Multiple Inheritance (via interfaces)

Explain the concept of method overriding in Java.

• Method overriding allows a subclass to provide a specific implementation of a method already defined in its superclass.

• Method overriding is when a superclass changes the implementation of a method in its subclass.

• Method overriding allows a class to inherit methods from multiple superclasses.

• Method overriding is a way to create new methods in a class without affecting the superclass.

What is the purpose of an abstract class in Java?

• To provide a complete implementation of all methods for subclasses.

• To provide a base class with common functionality and enforce a contract for subclasses.

• To define methods that cannot be overridden by subclasses.

• To create a new instance of a class directly.

How do interfaces differ from abstract classes in Java?

• Interfaces can contain implemented methods, while abstract classes only have method signatures.

• Abstract classes support multiple inheritance, while interfaces do not.

• Interfaces can have instance variables, while abstract classes cannot.

• Interfaces allow multiple inheritance and only contain method signatures, while abstract classes can have implemented methods and instance variables.

What is the super keyword used for in Java?

• The super keyword is used to access methods and constructors of the parent class.

• The super keyword is used to delete parent class methods.

• The super keyword is used to access static variables of the parent class.

• The super keyword is used to create new classes.

Can a class implement multiple interfaces in Java?

• A class can only implement one interface in Java.

• Yes, a class can implement multiple interfaces in Java.

• A class can extend multiple classes in Java.

• Interfaces cannot be implemented by classes in Java.

What happens if a subclass does not override a method from its superclass?

• The subclass cannot access the method from its superclass.

• The subclass inherits the method from its superclass.

• The subclass creates a new method with the same name.

• The subclass will throw an error when calling the method.

Define single inheritance and give an example in Java.

• class Plant { void grow() { System.out.println("Growing"); }} class Flower extends Plant { void bloom() { System.out.println("Blooming"); }}

• class Vehicle { void drive() { System.out.println("Driving"); }} class Car extends Vehicle { void honk() { System.out.println("Honking"); }}

• Example: class Animal { void eat() { System.out.println("Eating"); }} class Dog extends Animal { void bark() { System.out.println("Barking"); }}

• class Animal { void run() { System.out.println("Running"); }} class Cat extends Animal { void meow() { System.out.println("Meowing"); }}

What is the significance of the 'abstract' keyword in a class declaration?

• The 'abstract' keyword is used to define a class that cannot have any methods.

• The 'abstract' keyword signifies that a class cannot be instantiated and may contain abstract methods that must be implemented by subclasses.

• The 'abstract' keyword allows a class to be instantiated directly.

• The 'abstract' keyword indicates that a class can only contain concrete methods.

How can you call a superclass method from a subclass?

• Call the superclass method directly without any prefix.

• Use 'super.methodName()' in the subclass.

• Use 'this.methodName()' in the subclass.

• Override the superclass method in the subclass.