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 |
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 |
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 |
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 |