Java quiz 28: Object values as parameters

<< Java Quizzes    Green = Easy,  Blue = Normal,  Red = Hard
 01   02   03   04   05   06   07   08   09   10   11   12   13   14   15   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31   32   33   By title 
>>

Java quiz 28: Object values as parameters

Level: Normal

What is the output of the following code?

public class MyClass
{
  static void myMethod(StringBuffer s1, StringBuffer s2)
  {
    s1.append("h");
    s2.append("k");
    s1 = new StringBuffer("x");
    s2 = s1;
  }
  public static void main(String[] args)
  {
    StringBuffer sb1 = new StringBuffer("m");
    StringBuffer sb2 = new StringBuffer("o");
    myMethod(sb1, sb2);
    System.out.print(sb1 + ", " + sb2);
  }
}
Author: Sar Maroof

a. This program writes “mh, ok” to the standard output.
b. This program writes “mx, ox” to the standard output.
c. This program writes “h, k” to the standard output.
d. This program writes “m, o” to the standard output.
e. This program writes nothing to the standard output.
f. Runtime exception.
g. This code fails to compile.

Answer explanation

We actually passed the values of the objects sb1 and sb2 not their references to the method myMethod, Therefore,
the statements
s1 = new StringBuffer(“x”); and s2 = s1; don’t affect the output of the program.

The correct answer is: a.

If you found this difficult, you might consider reading my book Java quizmaster for beginners. It is easy to understand, organized to learn Java in 17 days and it guides you to master Java code by solving 105 quizzes and 117 assignments. This book explains each chapter properly before starting with exercises and assignments. It is available on Amazon. See inside the book here!

Please, leave your questions, feedback and suggestions in the comments below!
SarMaroof.com offers a practical method to learn and improve your Java skills. It avoids unnecessary long boring theoretical explanations, but it uses many exercises and quizzes.




Sar Maroof is graduated from HBO Amsterdam "higher professional education". He is a professional computer programming teacher, gives master classes and publishes technical articles. His experience with developing software started from 2001 and he has worked as a software developer for several big as well as small companies and later as a freelancer. He is the author of Java quizmaster and Build a Java application in 7 days.

Books by Sar Maroof

           

 Subscribe to Sar Maroof's RSS feeds!
 Mail this page to a friend!
 Bookmark this page!

Leave a Reply

Your email address will not be published. Required fields are marked *