The For Statement

The 'for' loop is more compact than the 'while' and 'do' loops and automatically updates the loop counter at the end of each iteration. Both 'for' and 'while' loops are designed for different situations. You'll learn more about when to use each later.

13. Sentinel Controlled Loop


Answer:

Yes. Now the test part of the for will look for the sentinel.

Sentinel Controlled Loop

In a sentinel controlled loop the change part depends on data from the user. It is awkward to do this inside a for statement. So the change part is omitted from the for statement and put in a convenient location.

Below is an example. The program keeps asking the user for x and printing the square root of x. The program ends when the user enters a negative number.

This program would be better if a while statement were used in place of the for statement.

import java.util.Scanner;

public class EvalSqrt
{
  public static void main (String[] args )
  {
    Scanner scan = new Scanner( System.in );
    double x;

    System.out.print("Enter a value for x or -1 to exit: ")  ;
    x = scan.nextDouble();

    for (    ; x >= 0.0 ;   )  
    {
      System.out.println( "Square root of " + x + " is " + Math.sqrt( x ) ); 

      System.out.print("Enter a value for x or -1 to exit: ")  ;
      x =  scan.nextDouble();
    }
  }
}

Question 13:

Do you think that the test part of a for can be omitted?