<< Chapter < Page Chapter >> Page >
Part of a self-assessment test designed to help you determine how much you know about extending classes, overriding methods, and polymorphic behavior in Java.

Table of contents

Preface

This module is part of a self-assessment test designed to help you determine how much you know about object-orientedprogramming using Java.

The test consists of a series of questions with answers and explanations of the answers.

The questions and the answers are connected by hyperlinks to make it easy for you to navigate from the question to the answer and back.

I recommend that you open another copy of this document in a separate browser window and use the links to under Listings to easily find and view the listings while you are reading about them.

Questions

Question 1 .

What output is produced by the program shown in Listing 1 ?

  • A. Compiler Error
  • B. Runtime Error
  • C. A
  • D. None of the above.
Listing 1 . Listing for Question 1.
public class Ap120{ public static void main(String args[]){new Worker().doIt(); }//end main()}//end class Ap120 class Worker{void doIt(){ Base myVar = new A();myVar.test(); System.out.println("");}//end doIt() }// end class Workerclass Base{ }//end class Baseclass A extends Base{ public void test(){System.out.print("A "); }//end test()}//end class A

Answer and Explanation

Question 2

What output is produced by the program shown in Listing 2 ?

  • A. Compiler Error
  • B. Runtime Error
  • C. A
  • D. None of the above.
Listing 2 . Listing for Question 2.
public class Ap121{ public static void main(String args[]){new Worker().doIt(); }//end main()}//end class Ap121 class Worker{void doIt(){ Base myVar = new A();((A)myVar).test(); System.out.println("");}//end doIt() }// end class Workerclass Base{ }//end class Baseclass A extends Base{ public void test(){System.out.print("A "); }//end test()}//end class A

Answer and Explanation

Question 3

What output is produced by the program shown in Listing 3 ?

  • A. Compiler Error
  • B. Runtime Error
  • C. A
  • D. None of the above.
Listing 3 . Listing for Question 3.
public class Ap122{ public static void main(String args[]){new Worker().doIt(); }//end main()}//end class Ap122 class Worker{void doIt(){ Base myVar = new A();myVar.test(); System.out.println("");}//end doIt() }// end class Workerclass Base{ abstract public void test();}//end class Base class A extends Base{public void test(){ System.out.print("A ");}//end test() }//end class A

Answer and Explanation

Question 4

What output is produced by the program shown in Listing 4 ?

  • A. Compiler Error
  • B. Runtime Error
  • C. A
  • D. None of the above.
Listing 4 . Listing for Question 4.
public class Ap123{ public static void main(String args[]){new Worker().doIt(); }//end main()}//end class Ap123 class Worker{void doIt(){ Base myVar = new A();myVar.test(); System.out.println("");}//end doIt() }// end class Workerabstract class Base{ abstract public void test();}//end class Base class A extends Base{public void test(){ System.out.print("A ");}//end test() }//end class A

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Object-oriented programming (oop) with java' conversation and receive update notifications?

Ask