Java puzzle 14: Understanding while loops

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If this code is compiled and run, it writes 777 to the standard output. By adding only one statement on the line 10 the code writes 641 to the standard output.

What is that statement?

Java puzzle 14: Understanding while loops

Level: Normal

public class MyClass
{
  public static void main(String[] args)
  {
    int i = 0;
    int x = 7;
    while(i < 3)
    {
      i++;
      // add your statement here!
      System.out.print(x);
    }
  }
}
Author: Sar Maroof

Answer explanation

  1. The program writes 777 to the standard output. We need to decrement the value of x first by one and then by 2 and at last by 3 to change the result from 777 to 641.
  2. The easiest way to achieve that is to decrement the value of x by the value of i.
  3. By the first execution of the loop, the value of the variable i is 1,  by the next execution is 2 and at last its value is 3.
  4. The correct statement is: x -= i;





Sar Maroof is a professional software development teacher, gives master classes and publishes technical articles. He is also an expert software developer and worked for several big as well as small companies and later as a freelancer.

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