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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.
What output is produced by the program shown in Listing 1 ?
| Listing 1 . Listing for Question 1. |
|---|
public class Ap151{
public static void main(String args[]){new Worker().doIt();
}//end main()}//end class Ap151
class Worker{void doIt(){
Object refA = new MyClassA();Object refB =
(Object)(new MyClassB());System.out.print(refA);
System.out.print(refB);System.out.println("");
}//end doIt()}// end class Worker
class MyClassA{public String toString(){
return "OK ";}//end test()
}//end class MyClassAclass MyClassB{
public String toString(){return "OK ";
}//end test()}//end class MyClassB |
What output is produced by the program shown in Listing 2 ?
| Listing 2 . Listing for Question 2. |
|---|
public class Ap152{
public static void main(String args[]){
new Worker().doIt();}//end main()
}//end class Ap152class Worker{
void doIt(){Object ref1 = new MyClassA();
Object ref2 = new MyClassB();System.out.print(ref1);MyClassB ref3 = (MyClassB)ref1;
System.out.print(ref3);System.out.println("");
}//end doIt()}// end class Worker
class MyClassA{public String toString(){
return "OK ";}//end test()
}//end class MyClassAclass MyClassB{
public String toString(){return "OK ";
}//end test()}//end class MyClassB |
What output is produced by the program shown in Listing 3 ?
| Listing 3 . Listing for Question 3. |
|---|
import java.util.Random;
import java.util.Date;public class Ap153{
public static void main(String args[]){new Worker().doIt();
}//end main()}//end class Ap153
class Worker{void doIt(){
Random ref = new Random(new Date().getTime());
if(ref.nextBoolean()){throw new IllegalStateException();
}else{System.out.println("OK");
}//end else}//end doIt()
}// end class Worker |
What output is produced by the program shown in Listing 4 ?
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