Code Snippets-based MCQs

Inheritance

Table of contents

Easy Level MCQs
Slightly harder MCQs
Tricky MCQs

Easy Level MCQs

What will be the output of this code?

 class Parent {
     String name = "Parent";

     Parent() {
         System.out.println("Parent Constructor");
     }
 }

 class Child extends Parent {
     String name = "Child";

     Child() {
         System.out.println("Child Constructor");
     }
 }

 public class Main {
     public static void main(String[] args) {
         Child child = new Child();
         System.out.println(child.name);
     }
 }

Answer

Parent Constructor Child Constructor Child

What will be the output of this code?

class Example {
    static int x = 10;

    static void print() {
        System.out.println(x);
    }
}

public class Main {
    public static void main(String[] args) {
        Example.x = 20;
        Example.print();
    }
}

Answer

What will be the output of this code?

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

class B extends A {
    static void display() {
        System.out.println("B");
    }
}

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

Answer

What will be the output of this code?

class Test {
    int x;

    Test() {
        this(10);
        System.out.println("No-arg constructor");
    }

    Test(int x) {
        this.x = x;
        System.out.println("Parameterized constructor");
    }
}

public class Main {
    public static void main(String[] args) {
        Test t = new Test();
    }
}

Answer

Parameterized constructor No-arg constructor

What will be the output of this code?

class Test {
    final int x;

    Test(int x) {
        this.x = x;
    }

    void display() {
        System.out.println(x);
    }
}

public class Main {
    public static void main(String[] args) {
        Test t = new Test(5);
        t.display();
    }
}

What will be the output of this code?

Answer

What will be the output of this code?

class Test {
    void method(int a) {
        System.out.println("int");
    }

    void method(double a) {
        System.out.println("double");
    }
}

public class Main {
    public static void main(String[] args) {
        Test t = new Test();
        t.method(5.0);
    }
}

Answer

double

What will be the output of this code?

 class Test {
     void method() {
         System.out.println("Test Method");
     }
 }

 public class Main {
     public static void main(String[] args) {
         Test t1 = new Test();
         Test t2 = t1;
         t2.method();
     }
 }

Answer

Test Method

What will be the output of this code?

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

 class Dog extends Animal {
 }

 public class Main {
     public static void main(String[] args) {
         Dog dog = new Dog();
         dog.makeSound();
     }
 }

Answer

Animal sound

What will be the output of this code?

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

 class Cat extends Animal {
     void makeSound() {
         System.out.println("Meow");
     }
 }

 public class Main {
     public static void main(String[] args) {
         Cat cat = new Cat();
         cat.makeSound();
     }
 }

Answer

Meow

What will be the output of this code?

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

class Child extends Parent {
}

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

Answer

Parent class

What will be the output of this code?

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

class Child extends Parent {
    Child() {
        System.out.println("Child Constructor");
    }
}

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

Answer

Parent Constructor Child Constructor

What will be the output of this code?

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

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

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

Answer

Parent Child

What will be the output of this code?

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

class Child extends Parent {
    void message() {
        System.out.println("Child message");
    }

    void parentMessage() {
        super.message();
    }
}

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

Answer

Parent message

What will be the output of this code?

class Parent {
    public int number = 5;
}

class Child extends Parent {
    void show() {
        System.out.println(number);
    }
}

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

Answer

What will be the output of this code?

class Parent {
    public String toString() {
        return "Parent class";
    }
}

class Child extends Parent {
}

public class Main {
    public static void main(String[] args) {
        Child child = new Child();
        System.out.println(child);
    }
}

Answer

Parent class

What will be the output of this code?

class Vehicle {
    void start() {
        System.out.println("Vehicle started");
    }
}

class Car extends Vehicle {
    void start() {
        System.out.println("Car started");
    }
}

public class Main {
    public static void main(String[] args) {
        Car car = new Car();
        car.start();
    }
}

Answer

Car started

What will be the output of this code?

class Parent {
    protected int number = 10;
}

class Child extends Parent {
    void display() {
        System.out.println(number);
    }
}

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

Answer

Slightly Harder MCQs

What will be the output of this code?

class Parent {
    int value() {
        return 1;
    }
}

class Child extends Parent {
    double value() {
        return 2.0;
    }
}

public class Main {
    public static void main(String[] args) {
        Parent obj = new Child();
        System.out.println(obj.value());
    }
}

Answer

Compile-time error

What will be the output of this code?

 class Parent {
     int number = 5;
 }

 class Child extends Parent {
     int number = 10;

     void display() {
         System.out.println(number);
         System.out.println(super.number);
     }
 }

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

Answer

10 5

What will be the output of this code?

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

 class Child extends Parent {
     Child() {
         super();
         System.out.println("Child Constructor");
     }
 }

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

Answer

Parent Constructor Child Constructor

What will be the output of this code?

 class Parent {
     void display(int num) {
         System.out.println("Number: " + num);
     }
 }

 class Child extends Parent {
     void display(String str) {
         System.out.println("String: " + str);
     }
 }

 public class Main {
     public static void main(String[] args) {
         Child child = new Child();
         child.display(10);
         child.display("Hello");
     }
 }

Answer

Number: 10 String: Hello

What will be the output of this code?

 class Parent {
     Parent(int x) {
         System.out.println("Parent Constructor with value: " + x);
     }
 }

 class Child extends Parent {
     Child(int x) {
         super(x);
         System.out.println("Child Constructor with value: " + x);
     }
 }

 public class Main {
     public static void main(String[] args) {
         Child child = new Child(5);
     }
 }

Answer

Parent Constructor with value: 5 Child Constructor with value: 5

Tricky MCQs

What will be the output of this code?

 public class Main {
     public static void main(String[] args) {
         String s1 = "Hello";
         String s2 = "Hello";
         String s3 = new String("Hello");
         System.out.println(s1 == s2);
         System.out.println(s1 == s3);
     }
 }

 <summary>Answer</summary>
 true false

What will be the output of this code?

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

public class Main {
    public static void main(String[] args) {
        A obj = null;
        obj.method();
    }
}

<summary>Answer</summary>
NullPointerException

What will be the output of this code?

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

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

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

Answer

Child show

What will be the output of this code?

 class Parent {
     int number = 5;
 }

 class Child extends Parent {
     int number = 10;

     void display() {
         System.out.println(number);
     }
 }

 public class Main {
     public static void main(String[] args) {
         Parent parent = new Child();
         parent.display();
     }
 }

Answer

Compile-time error

What will be the output of this code?

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

 class Child extends Parent {
     Child() {
         this(10);
         System.out.println("Child Constructor");
     }

     Child(int x) {
         System.out.println("Child Constructor with value: " + x);
     }
 }

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

Answer

Parent Constructor Child Constructor with value: 10 Child Constructor

What will be the output of this code?

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

 class Child extends Parent {
     void display() {
         System.out.println("Child display");
     }
 }

 public class Main {
     public static void main(String[] args) {
         Parent parent = new Child();
         parent.display();
     }
 }

Answer

Child display

What will be the output of this code?

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

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

 class Child extends Parent {
     Child() {
         System.out.println("Child Constructor");
     }

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

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

Answer

Parent Constructor Child show Child Constructor

What is the issue in this code?
```
 class Parent {
     Parent(int x) {
         System.out.println("Parent Constructor");
     }
 }

 class Child extends Parent {
     Child() {
         System.out.println("Child Constructor");
     }
 }
```
The `super()` call is missing in the `Child` constructor
The `Child` constructor should take an argument
The `Parent` constructor should have a no-argument constructor
There is no issue in the code

Answer

The super() call is missing in the Child constructor
What is the issue in this code?
```
 class Parent {
     void display(int x) {
         System.out.println("Parent: " + x);
     }
 }

 class Child extends Parent {
     void display(String x) {
         System.out.println("Child: " + x);
     }
 }
```
Method `display` in `Child` should override `display` in `Parent`
The `display` method in `Child` is not an override, it's an overload
The `Parent` class should be declared as abstract
There is no issue in the code

Answer

The display method in Child is not an override, it’s an overload
What is the issue in this code?
```
 class Parent {
     int value() {
         return 10;
     }
 }

 class Child extends Parent {
     double value() {
         return 10.0;
     }
 }
```
The `value` method in `Child` has an incompatible return type
The `value` method in `Parent` should return `double`
The `Child` class must use `super.value()`
There is no issue in the code

Answer

The value method in Child has an incompatible return type

What is the issue in this code?

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

 class Child extends Parent {
     Child() {
         System.out.println("Child Constructor");
         super();
     }
 }

Answer

super() should be the first statement in the Child constructor

What is the issue in this code?
```
 class Parent {
     private void show() {
         System.out.println("Parent show");
     }
 }

 class Child extends Parent {
     void show() {
         System.out.println("Child show");
     }
 }
```
The `show` method in `Child` does not override the `show` method in `Parent`
The `show` method in `Parent` should be protected
The `Child` class cannot define a method with the same name
There is no issue in the code

Answer

The show method in Child does not override the show method in Parent
What is the issue in this code?
```
 class Parent {
     final void display() {
         System.out.println("Parent display");
     }
 }

 class Child extends Parent {
     void display() {
         System.out.println("Child display");
     }
 }
```
The `display` method in `Child` cannot override the final method in `Parent`
The `display` method in `Parent` should not be final
The `Child` class should extend a different class
There is no issue in the code

Answer

The display method in Child cannot override the final method in Parent
What is the issue in this code?
```
 class Parent {
     private Parent() {
         System.out.println("Parent Constructor");
     }
 }

 class Child extends Parent {
     Child() {
         System.out.println("Child Constructor");
     }
 }
```
The `Parent` constructor is private and cannot be accessed by `Child`
The `Child` constructor should be private
The `Parent` constructor should be protected
There is no issue in the code

Answer

The Parent constructor is private and cannot be accessed by Child

What is the issue in this code?

 class Parent {
     Parent() {
         this(10);
     }

     Parent(int x) {
         System.out.println("Parent Constructor with value: " + x);
     }
 }

 class Child extends Parent {
     Child() {
         System.out.println("Child Constructor");
     }
 }

Answer

Recursive constructor invocation in Parent class

What is the issue in this code?
```
 class Parent {
     void display() {
         System.out.println("Parent display");
     }
 }

 class Child extends Parent {
     void display(int x) {
         System.out.println("Child display: " + x);
     }
 }
```
Method ``display(int x)`` in `Child` does not override `display()` in `Parent`
Method `display(int x)` should be private
The `Parent` class should take an argument
There is no issue in the code

Answer

Method display(int x) in Child does not override display() in Parent