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Answer and Explanation

Question 10

What output is produced by the program shown in Listing 10 ?

  • A. Compiler Error
  • B. Runtime Error
  • C. Base
  • D. A B
  • E. None of the above.
Listing 10 . Listing for Question 10.
public class Ap129{ public static void main(String args[]){new Worker().doIt(); }//end main()}//end class Ap129 class Worker{void doIt(){ Base myVar = new A();myVar.test(); myVar = new B();myVar.test(); System.out.println("");}//end doIt() }// end class Workerclass Base{ public void test(){System.out.print("Base ");}; }//end class Baseclass A extends Base{ public void test(){System.out.print("A "); }//end test()}//end class A class B extends Base{public void test(){ System.out.print("B ");}//end test() }//end class B

Answer and Explanation

Listings

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Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Ap0110: Self-assessment, Extending classes, overriding methods, and polymorphic behavior
  • File: Ap0110.htm
  • Originally published: 2002
  • Published at cnx.org: 12/08/12
  • Revised: 12/03/14
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Answers

Answer 10

D. A B

Explanation 10

Another illustration of simple polymorphic behavior

In this program, two classes named A and B extend the class named Base , each overriding the method named test to produce different behavior. (Typically, overridden methods in different classes will produce different behavior, even though they have the same names.)

Behavior appropriate for object on which method is called

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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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