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.


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Java quizmaster for beginners (English)

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Sar Maroof is the author of two Java books namely, Java quizmaster for beginners and A guide to build a Java application.
Experience with developing web applications since 2001
Sun Certified JSP as well as EJB
CIW Certified Internet Webmaster
Applied Science in Physics HBO Amsterdam
As well as Bachellor Science in Physics.

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