Counter-Controlled While Loop - Java Sample Program

//Counter-controlled while loop
//Filename: CounterControlledWhileLoop

import java.util.*;

public class CounterControlledWhileLoop
{
static Scanner console = new Scanner(System.in);

public static void main(String[] args)
{
int limit; //store the number of items in the list
int number; //variable to store the number
int sum; //variable to store the sum
int counter; //loop control variable

System.out.print("Line 1: Enter the number of " + "integers in the list: "); //Line 1
limit = console.nextInt(); //Line 2
System.out.println(); //Line 3
sum = 0; //Line 4
counter = 0; //Line 5
System.out.println("Line 6: Enter " + limit + " integers."); //Line 6

while (counter < limit) //Line 7
{
number = console.nextInt(); //Line 8
sum = sum + number; //Line 9
counter++; //Line 10
}

System.out.printf("Line 11: The sum of the %d " + "numbers = %d%n", limit, sum); //Line 11

if (counter != 0) //Line 12
System.out.printf("Line 13: The average = %d%n",(sum / counter)); //Line 13
else //Line 14
System.out.println("Line 15: No input."); //Line 15
}
}

/*
Sample Output: 
In this sample run, the user input is shaded.
*********************************************************
Line 1: Enter the number of integers in the list: 12
Line 6: Enter 12 integers.
8 9 2 3 90 38 56 8 23 89 7 2
Line 11: The sum of the 12 numbers = 335
Line 13: The average = 27
*********************************************************

Explanation:
 The preceding program works as follows: The statement in Line 1 prompts the user to
input the data for processing. The statement in Line 2 reads the next input and stores it in
the variable limit. The value of limit indicates the number of items to be read. The
statements in Lines 4 and 5 initialize the variables sum and counter to 0. The while
statement in Line 7 checks the value of counter to determine how many items have
been read. If counter is less than limit, the while loop proceeds for the next iteration.

 The statement in Line 8 stores the next number in the variable number. The statement in
Line 9 updates the value of sum by adding the value of number to the previous value. The
statement in Line 10 increments the value of counter by 1. The statement in Line 11
outputs the sum of the numbers. The statements in Lines 12 through 15 output either the
average or the text: Line 15: No input.

 Note that in this program, in Line 4, sum is initialized to 0. In Line 9, after storing the
next number in number in Line 8, the program adds the next number to the sum of all
the numbers scanned before the current number. The first number read is added to zero
(because sum is initialized to 0), giving the correct sum of the first number. To find the
average, divide sum by counter. If counter is 0, then dividing by 0 terminates the
program and you get an error message. Therefore, before dividing sum by counter, you
must check whether or not counter is 0.

 Notice that in this program, the statement in Line 5 initializes the LCV counter to 0.
The expression counter < limit in Line 7 evaluates whether counter is less than
limit. The statement in Line 8 updates the value of counter. Note that in this program,
the while loop can also be written without using the variable number as follows:
while (counter < limit)
{
sum = sum + console.nextInt();
counter++;
}
*/