Beginner quizzes – Java abstract classes

The following Java exercise(s) are designed for beginner level programmers. If the level is too hard, then I recommend reading my article about this topic, which offers a theoretical explanation including more exercises. Read More: Java Abstract Classes

abstract-classes-green

Quiz 1: Extending an abstract class

What happens when the following program is compiled and run?

public abstract class MyAbstract {

	abstract int getSum();
	abstract int getSum(int x);
	abstract int getSum(int x, int y);
}

public abstract class Sub extends MyAbstract {

	int x = 4;

	int getSum(){
		return x + x;
	}
	int getSum(int x){
		return x + x;
	}
	int getSum(int x, int y){
		int z = x + y;
		System.out.print(z);
		return z;
	}
	public static void main(String[] args){
		Sub sub = new Sub();
		sub.getSum(4,2);
	}
}

Select the correct answer.


Quiz 2: Abstract classes in Java

What happens when the following program is compiled and run?

public abstract class AbstractClass {

	int b = 6;

	abstract int getNumber(int c, int d);
}

public class Sub extends AbstractClass {

	int b = 2;

	Sub() {
		b = super.b;
	}
	int getNumber(int x, int y){
		int i = x - y + b;
		System.out.print(i);
		return i;
	}
	public static void main(String[] args){
		Sub sub = new Sub();
		sub.getNumber(7,3);
	}
}

Select the correct answer.


Please, leave your questions, feedback and suggestions in the comments below!
SarMaroof.com offers a practical method to learn and improve your Java skills. It avoids unnecessary long boring theoretical explanations, but it uses many exercises and quizzes.



Sar Maroof is graduated from HBO Amsterdam “higher professional education” when he already had a bachelor of science degree in Physics.
He is a SUN certified JSP as well as EJB. He has experience with Java since 2001 and worked for several big as well as small companies and later as a freelancer.
He is the author of Java quizmaster and Build a Java application in 7 days.

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