Java MCQ – Interfaces – Part 2

This collection of Java Multiple Choice Questions and Answers (MCQs): Quizzes & Practice Tests with Answer focuses on “Java Interfaces”.
 

1. What happens when a constructor is defined for an interface?

A Compilation failure

B An exception is thrown

C The interface compiles successfully

D The class implementing the interface will throw an exception

Answer  

2. What happen if we provide the implementation of a method in an interface?

A The class implementing this method does not need to provide the implementation for this method.

B An exception is thrown

C Compilation failure

D None of the above

Answer  

3. What happens when we access the same variable defined in two interfaces implemented by the same class?

A An exception is thrown

B Compilation failure

C JVM is unable to identify the correct variable

D interfaceName.variableName must be defined

Answer [st_adsense]  

4. What’s wrong with the following code?

interface Vehicle {
	void start();

	void run();

	void stop();
}

class Car implements Vehicle {
	
	public void start() {
	}
}

A Compilation error

B Runtime error

C An exception is thrown

D Source code is correct

Answer  

5. What is the output of the following code?

interface A
{
    int var = 2;
}
class B implements A 
{
    void show()
    {
    	var = 3;
    	System.out.println("var = "+var);
    }
}
public class Main {
	public static void main(String[] args) {
		B obj = new B();
		obj.show();	
	}
}

A 2

B 3

C 5

D Compilation error

Answer  

6. Which statement is correct about interfaces in Java?

A The interface is used to perform multiple inheritance in java.

B We cannot instantiate an interface.

C An interface can inherit from another interface.

D All the answers are true

Answer  

7. Which statement is wrong about interfaces in Java?

A It is used to achieve abstraction and multiple inheritance in Java.

B It can be instantiated, that means we can create an object from an interface.

C We can only have abstract methods in the interface.

D All the answers are false.

Answer [st_adsense]  

8. What is the output of the following code?

interface A
{
    void show();
}
class B implements A 
{
    public void show()
    {
    	System.out.println("Welcome To StackHowTo!");
    }
}
public class Main {
	public static void main(String[] args) {
		A obj = new B();
		obj.show();	
	}
}

A We cannot create the object ‘obj’ from the interface ‘A’.

B Welcome To StackHowTo!

C Compilation error

D All the answers are false.

Answer  

9. Java interface is used for __________

A Implementing the behavior of multiple inheritance

B Achieving loose coupling

C Achieving abstraction

D All the answers are true

Answer  

10. Which of the following statements contains only unimplemented methods?

A Class

B Abstract class

C Interface

D None of the above

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