Interfaces Interview Questions Mock Test

Question 1: JAVA OOPS - Interface Basics

Which of the following is true about interfaces in Java?

Question 2: JAVA OOPS - Implementing Interface

What will be printed?

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

Question 3: JAVA OOPS - Multiple Interface Implementation

Which of the following is correct?

interface A { void showA(); }
interface B { void showB(); }
class C implements A, B {
    public void showA() { System.out.println("A"); }
    public void showB() { System.out.println("B"); }
}

Question 4: JAVA OOPS - Default Methods in Interface

Which is true about default methods in Java interfaces?

Question 5: JAVA OOPS - Interface Reference

Which statement is correct?

interface A { void show(); }
class B implements A { public void show() { System.out.println("Hi"); } }

Question 6: JAVA OOPS - Interface with Variables

Which of the following statements is true?

Question 7: JAVA OOPS - Interface and Abstract Class

Which is true?

Question 8: JAVA OOPS - Static Methods in Interface

Which is valid in Java 8+?

interface Demo {
    static void show() { System.out.println("Hello"); }
}
public class Main {
    public static void main(String[] args) {
        Demo.show();
    }
}

Question 9: JAVA OOPS - Interface Inheritance

Which of the following is correct?

Question 10: JAVA OOPS - Purpose of Interface

What is the main purpose of interfaces in Java?