Descriptive Question

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Submitted by heartin on Mon, 09/14/2015 - 10:49

QID:

Type:

Descriptive Question

Category:

Java Programmer I

Tags:

inheritance

overriding

rtti

Question:

Given:

public class X implements Z {

public String toString() {

return "I am X";

}

public static void main(String[] args) {

Y myY = new Y();

X myX = myY;

Z myZ = myX;

System.out.println(myZ);

}

}

class Y extends X {

public String toString() {

return "I am Y";

}

}

interface Z {}

What is the reference type of myZ and what is the type of the object it references?

Answer and Explanation (Click to expand)

Answer:

Here, both reference type and object type is Y.

Explanation:

We are creating only one object here using new Y() and then assigning it to different parent type variables. So object type is Y.

Classes and arrays are known as reference types in Java. Since the object is Y(), the reference type is also Y. We can verify this by adding a simple print statement as:

System.out.println(myZ.getClass().getName());

This will print:

com.javajee.Y

The getClass method Returns the runtime class of an object.

Q&A Set:

Set X

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