Beginner quizzes – Java casting object

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 Object Casting

Article: Java casting object Quizzes: Beginner  Intermediate  Advanced

Quiz 1: Upcasting an object

What happens when the following program is compiled and run?

public class Super {

	protected int i = 4;

	public int method(){
		return i * i;
	}
}

public class Sub extends Super {

	int i = 3;

	public int method(){
		return i * i;
	}
	public static void main(String[] args){
		Super s = new Sub();
		System.out.print("-x" + s.method());
		System.out.print("-x" + s.i);
	}
}

Quiz 2: Downcasting and upcasting objects in Java

What happens when the following program is compiled and run?

public class MySuper {

	int z = 3;

	int myMethod(){
		return z;
	}
}

public class MySub extends MySuper {

	int z = 8;

	int myMethod(){
		return z;
	}
	public static void main(String[] args){
		MySuper mySuper = new MySub();
		MySub mySub = (MySub) mySuper;
		System.out.print("-x" + mySuper.myMethod() + "-x" + mySuper.z);
		System.out.print("-x" + mySub.myMethod() + "-x" + mySub.z);
	}
}

Article: Java casting object 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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