Partial abstraction in Java - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an abstract class named Vehicle.

Java

public [1] class Vehicle {
    // class body
}

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

Aprivate

Bfinal

Cstatic

Dabstract

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'final' instead of 'abstract' will prevent the class from being subclassed.

Using 'static' or 'private' keywords here is incorrect for class declaration.

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

2fill in blank

medium

Complete the code to declare an abstract method named startEngine in the Vehicle class.

Java

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

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

Aabstract

Bstatic

Cfinal

Dprivate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'final' or 'static' keywords with abstract methods is not allowed.

Forgetting the semicolon at the end of the method declaration.

The abstract keyword is used to declare an abstract method without a body.

3fill in blank

hard

Fix the error in the subclass Car that extends Vehicle by correctly overriding the abstract method startEngine.

Java

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

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

AstartEngine()

BstartEngine(void)

CstartEngine

DstartEngine[]

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting parentheses after the method name causes a syntax error.

Using incorrect parameter syntax like 'void' inside parentheses.

The method name must include parentheses () to correctly override the abstract method.

4fill in blank

hard

Fill both blanks to declare an abstract class Shape with an abstract method draw.

Java

public [1] class Shape {
    public [2] void draw();
}

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

Aabstract

Bfinal

Dstatic

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'final' or 'static' keywords instead of 'abstract' for class or method.

Providing a method body for an abstract method.

The class must be declared abstract and the method abstract without a body.

5fill in blank

hard

Fill all three blanks to create a subclass Circle that extends Shape and implements the draw method.

Java

public class Circle extends [1] {
    @Override
    public void [2] {
        System.out.println([3]);
    }
}

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

AShape

Bdraw()

C"Drawing a circle"

DShape()

Attempts:

3 left

💡 Hint

Common Mistakes

Using constructor syntax 'Shape()' instead of class name in extends.

Omitting parentheses in method override.

Forgetting to put the message inside quotes.

The subclass extends the abstract class Shape, overrides the method draw(), and prints a message.