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

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.

a – This program does not compile.

b – This program writes “6” to the standard output.

c – This program writes “0” to the standard output.

d – This program writes “12” to the standard output.

e – This program writes “null” to the standard output.

f – This program writes nothing to the standard output.

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.

a – This program does not compile.

b – This program writes “2” to the standard output.

c – This program writes “0” to the standard output.

d – This program writes “10” to the standard output.

e – This program writes “6” to the standard output.

f – This program writes “null” to the standard output.

g – This program writes nothing to the standard output.

Article: Java abstract classes Quizzes: Beginner  Intermediate  Advanced

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Sar Maroof is a professional software development teacher, gives master classes and publishes technical articles. He is also an expert software developer and worked for several big as well as small companies and later as a freelancer.

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