CONTROL STRUCTURES II: REPETITION - Java Programming: From Problem Analysis to Program Design - page 258

EXAMPLE 5-4

Suppose you want to read some positive integers and average them, but you do not have
a preset number of data items in mind. Suppose you choose the number -999 to mark
the end of the data. You can proceed as follows:

//Sentinel-controlled while loop

import java.util.*;

public class SentinelControlledWhileLoop
{

static Scanner console = new Scanner(System.in);

static final int SENTINEL = -999;

public static void main(String[] args)
{

int number; //variable to store the number

int sum = 0; //variable to store the sum

int count = 0; //variable to store the total

//numbers read

System.out.println("Line 1: Enter positive integers "
+ "ending with " + SENTINEL); //Line 1

number = console.nextInt(); //Line 2

while (number != SENTINEL) //Line 3

{

sum = sum + number; //Line 4

count++; //Line 5

number = console.nextInt(); //Line 6

}

System.out.printf("Line 7: The sum of %d " +
"numbers = %d%n", count, sum); //Line 7

if (count != 0) //Line 8
System.out.printf("Line 9: The average = %d%n",
(sum / count));

//Line 9

else //Line 10

System.out.println("Line 11: No input."); //Line 11

}

}
Sample Run: (In this sample run, the user input is shaded.)

Line 1: Enter positive integers ending with -999
34 23 9 45 78 0 77 8 3 5 -999
Line 7: The sum of 10 numbers = 282
Line 9: The average = 28