Method overriding in Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of overridden method call

What is the output of the following Java code?

Java

class Animal {
    void sound() {
        System.out.println("Animal sound");
    }
}

class Dog extends Animal {
    @Override
    void sound() {
        System.out.println("Bark");
    }
}

public class Main {
    public static void main(String[] args) {
        Animal a = new Dog();
        a.sound();
    }
}

A Bark

B Runtime error

C Compilation error

D Animal sound

💡 Hint

Remember that the method called depends on the actual object type, not the reference type.

The variable 'a' is of type Animal but refers to a Dog object. The overridden method in Dog is called, so it prints 'Bark'.

❓ Predict Output

intermediate

Output with super keyword in overridden method

What will be printed when this Java program runs?

Java

class Parent {
    void show() {
        System.out.println("Parent show");
    }
}

class Child extends Parent {
    @Override
    void show() {
        System.out.println("Child show");
        super.show();
    }
}

public class Main {
    public static void main(String[] args) {
        Child c = new Child();
        c.show();
    }
}

A Child show

B

Child show
Parent show

C

Parent show
Child show

D Parent show

💡 Hint

The super keyword calls the parent class method inside the overridden method.

The Child's show method prints 'Child show' first, then calls super.show() which prints 'Parent show'.

🔧 Debug

advanced

Identify the error in method overriding

Which option correctly identifies the error in this code snippet?

Java

class Base {
    void display() {}
}

class Derived extends Base {
    int display() { return 1; }
}

A Runtime error due to return type mismatch

B Compilation error because method name is different

C No error, code runs fine

D Compilation error because return type int does not match void

💡 Hint

Check if the return type matches when overriding a method.

Overriding methods must have the same return type (or a subtype). Here, void and int differ, causing a compilation error.

🧠 Conceptual

advanced

Effect of private method on overriding

What happens if a method in the parent class is private and a method with the same signature is declared in the child class?

A The child method is a new method, no overriding occurs

B The child method overrides the parent private method

C Compilation error due to duplicate method

D Runtime error due to access violation

💡 Hint

Private methods are not visible to child classes.

Private methods are not inherited, so the child method is independent and does not override the parent method.

❓ Predict Output

expert

Output with method overriding and casting

What is the output of this Java program?

Java

class A {
    void print() {
        System.out.println("A");
    }
}

class B extends A {
    @Override
    void print() {
        System.out.println("B");
    }
}

class C extends B {
    @Override
    void print() {
        System.out.println("C");
    }
}

public class Main {
    public static void main(String[] args) {
        A obj = new C();
        ((B) obj).print();
    }
}

A ClassCastException at runtime

B B

C C

D A

💡 Hint

Casting does not change the actual object type; overridden method of actual object is called.

The object is of type C. Even when cast to B, the overridden print() in C is called, printing 'C'.