Java Inheritance and Abstraction

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Question 1

Which of the following statements about the Object class in Java is true?

A
Every Java class extends Object class either directly or indirectly.
B
Only classes without a superclass extend Object class.
C
The Object class cannot be extended.
D
Object class is an abstract class.

Question 2

What will be the output of the following code?

Java

class A {
    void display() {
        System.out.println("Class A");
    }
}
class B extends A {
    void display() {
        System.out.println("Class B");
    }
}
public class Main {
    public static void main(String[] args) {
        A obj = new B();
        obj.display();
    }
}

A
Class A
B
Class B
C
Compilation error
D
Runtime error

Question 3

Which keyword is used to create a subclass in Java?

A
implements
B
inherits
C
extends
D
interface

Question 4

What is abstraction in Java?

A
Hiding method names
B
Hiding internal implementation and showing only functionality
C
Creating private variables
D
Inheriting classes

Question 5

Which keyword is used to define an abstract class?

A
interface
B
abstract
C
static
D
private

Question 6

What happens if an abstract class does not have any abstract methods?

A
It will not compile.
B
The class can still be abstract.
C
Java will automatically provide an abstract method.
D
It becomes a concrete class.

Question 7

Which of the following statements about inheritance is false?

A
Java supports single inheritance.
B
Java allows multiple class inheritance using extends.
C
Interfaces can be used to achieve multiple inheritance.
D
The super keyword can be used to invoke the parent class constructor.

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