Java puzzle 01: A simple loop

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If this simple program is compiled and run, the following is written to the standard output.
-x1-x2-x3-x4-x5-x6-x7-x8-x9-x10

Add only one statement to the line 8. As a result of that the program writes “-x1-x7” to the standard output.

Java puzzle 1: A simple loop

Level: Normal

public class MyClass
{
  public static void main(String[] args)
  {
    for (int x = 1; x <= 10; x++)
    {
      System.out.print("-x" + x);
      // add a statement here!
    }
  }
}

Author: Sar Maroof

Answer explanation

  1. The loop of this program starts from the initial value of x = 1.
    each time the loop repeats, x++ increments the value of x by one until the value of x is equal to 9 or the conditional x<=10 returns false.
  2. We add the statement x += 5 on line 8. When the first time the loop is executed the statement System.out.print(“-x” + x); writes -x1 to the standard output. That is because the initial value of x is 1.
  3. The statement x += 5; increments the value of x by 5, then x++ increments the value of x by one.
  4. By the second execution of the loop, the value of x is equal to 7. The statement System.out.print(“-x” + x); writes -x7 to the standard output.
  5. The statement x +=5 increments the value of x by 5. Therefore the value of x becomes 12 and that is greater than 10. The conditional x <=10 returns false. Therefore the loop is terminated. The program writes: -x1-x7 to the standard output.

The answer is: x+=5;

public class MyClass
{
  public static void main(String[] args)
  {
    for (int x = 1; x <= 10; x++)
    {
      System.out.print("-x" + x);
      x+=5;
    }
  }
}

 

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Sar Maroof is graduated from HBO Amsterdam “higher professional education” when he already had a bachelor of science degree in Physics.
He is a SUN certified JSP as well as EJB. He has experience with Java since 2001 and worked 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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