for Loop Version

The for loop version also seems awkward. You have to remember that the "change" part of the for statement can be omitted. This is correct syntax, but now you must be careful to make the change in the loop body.

import java.io.* ;
class SqrtCalc
{
  public static void main( String[] args )
  {
    String chars;
    double x;
    Scanner scan = new Scanner(System.in );

    for ( chars = "yes"; chars.equals( "yes" );  )  // last part of "for" omitted
    {                                               // (this is OK)
      System.out.print("Enter a number-->");
      x = scan.nextDouble(); 
      chars = scan.nextLine();   // flush rest of the line
      System.out.println("Square root of " + x + " is " + Math.sqrt( x ) );
      System.out.print("Do you wish to continue? (yes or no) --> ");
      chars = scan.nextLine();
    }

  }
}

Of course, the biggest problem with all three versions is that the user must type exactly "yes" for the program to continue. Better programs would allow "y" or "Y" or "YES" .