Abstract vs concrete classes in Java - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an abstract class named Vehicle.

Java

public [1] class Vehicle {
    public abstract void start();
}

Drag options to blanks, or click blank then click option'

Astatic

Bfinal

Cabstract

Dpublic

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'final' instead of 'abstract' to declare the class.

Forgetting to use any keyword and making it a concrete class.

The keyword abstract is used to declare an abstract class in Java.

2fill in blank

medium

Complete the code to make the Car class inherit from the abstract Vehicle class.

Java

public class Car [1] Vehicle {
    @Override
    public void start() {
        System.out.println("Car started");
    }
}

Drag options to blanks, or click blank then click option'

Aextends

Binherits

Cimplements

Duses

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'implements' instead of 'extends' for class inheritance.

Using a non-existent keyword like 'inherits'.

In Java, a class inherits from another class using the extends keyword.

3fill in blank

hard

Fix the error in the code by completing the method declaration in the abstract class.

Java

public abstract class Animal {
    public [1] void makeSound();
}

Drag options to blanks, or click blank then click option'

Afinal

Babstract

Cstatic

Dprivate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'final' or 'static' keywords with abstract methods.

Forgetting to mark the method as abstract.

Abstract methods in an abstract class must be declared with the abstract keyword and have no body.

4fill in blank

hard

Fill both blanks to create a concrete class Dog that extends Animal and implements the makeSound method.

Java

public class Dog [1] Animal {
    @Override
    public void makeSound() [2] {
        System.out.println("Bark");
    }
}

Drag options to blanks, or click blank then click option'

Aextends

B()

C{}

Dimplements

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'implements' instead of 'extends' for class inheritance.

Using parentheses instead of curly braces for method body.

The class extends the abstract class, and the method body is enclosed in {}.

5fill in blank

hard

Fill all three blanks to create a concrete class Cat that extends Animal, implements makeSound, and adds a new method purr.

Java

public class Cat [1] Animal {
    @Override
    public void makeSound() [2] {
        System.out.println("Meow");
    }
    public void purr() [3] {
        System.out.println("Purr");
    }
}

Drag options to blanks, or click blank then click option'

Aextends

B()

C{}

Dimplements

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'implements' instead of 'extends' for class inheritance.

Using parentheses instead of curly braces for method bodies.

The class extends Animal, and both methods have bodies enclosed in {}.