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Part of a self-assessment test designed to help you determine how much you know about the super keyword, the final keyword, and static methods 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. 1, 2
  • D. 5, 10
  • E. None of the above
Listing 1 . Listing for Question 1.
public class Ap100{ public static void main(String args[]){new Worker().makeObj(); }//end main()}//end class definition class Worker{public void makeObj(){ Subclass obj = new Subclass();System.out.println(obj.getX() + ", " + obj.getY());}//end makeObj() }// end classclass Superclass{ private int x = 1;public Superclass(){x = 5; }//end constructorpublic int getX(){return x; }//end getX()}//end Superclass class Subclass extends Superclass{private int y = 2;public Subclass(){ super();y = 10; }//end constructorpublic int getY(){return y; }//end getY()}//end Subclass

Answer and Explanation

Question 2

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

  • A. Compiler Error
  • B. Runtime Error
  • C. 1, 2
  • D. 5, 2
  • E. 5, 10
  • F. 20, 10
  • G. None of the above
Listing 2 . Listing for Question 2.
public class Ap101{ public static void main(String args[]){new Worker().makeObj(); }//end main()}//end class definition class Worker{public void makeObj(){ Subclass obj = new Subclass();System.out.println(obj.getX() + ", " + obj.getY());}//end makeObj() }// end classclass Superclass{ private int x = 1;public Superclass(){x = 5; }//end constructorpublic Superclass(int x){this.x = x; }//end constructorpublic int getX(){return x; }//end getX()}//end Superclass class Subclass extends Superclass{private int y = 2;public Subclass(){ super(20);y = 10; }//end constructorpublic int getY(){return y; }//end getY()}//end Subclass

Answer and Explanation

Question 3

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

  • A. Compiler Error
  • B. Runtime Error
  • C. 5
  • D. None of the above
Listing 3 . Listing for Question 3.
public class Ap102{ public static void main(String args[]){new Worker().finalStuff(); }//end main()}//end class definition class Worker{public void finalStuff(){ final int x = 5;x = 10; System.out.println(x);}//end finalStuff() }// end class

Answer and Explanation

Question 4

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

  • A. Compiler Error
  • B. Runtime Error
  • C. 5
  • D. None of the above

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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
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