Java quiz 40: Method overriding

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This is an advanced quiz to test your skill on method overriding.

Java quiz 40: Method overriding

Level: Hard

What is the output of the following code?

public class MySuper
{
  int x = 1;
  
  public MySuper()
  {
    System.out.print(getResult(3));
  }
  int getResult()
  {
    return x;
  }
  int getResult(int i)
  {
    return(i + x + getResult() + x);
  }
}

public class MySub extends MySuper
{
  int getResult()
  {
    super.x = 5;
    return x + 3;
  }
  public static void main(String[] args)
  {
    new MySub();
  }
}
Author: Sar Maroof

Select the correct answer.

a. This program writes “19” to the standard output.
b. This program writes “13” to the standard output.
c. This program writes “6” to the standard output.
d. This program writes “17” to the standard output.
e. This program writes “16” to the standard output.

Answer explanation

  1. By creating the object of the type MySub, the constructor of the superclass MySuper is called.
  2. The statement System.out.print(getResult(3)); in the constructor is executed and the one-parameter method getResult is invoked.
  3. The method getResult(3) returns (i + x + getResult() + x);
    the parameter i is equal to 3.
    x is equal to 1. remember that after invoking the method getResult() which is overridden in MySub. The statement
    super.x = 5; reassigns the value 5 to the variable x.
    So, the overridden getResult() returns x + 3 = 8.
    The result is i + x + getResult() + x;
    And that is equal to 3 + 1 + 8 + 5 = 17

The correct answer is: d.

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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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