Java quiz 28: Object values as parameters

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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.

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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.

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