Summing in a loop

Summing works like counting, but instead of adding one each time, the loop adds the value it read. The sum starts at 0 before the loop:

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int total = 0;
        while (true) {
            int price = Integer.valueOf(scanner.nextLine());
            if (price == 0) {
                break;
            }
            total += price;
        }
        System.out.println("To pay: " + total);
    }
}

4
12
3
0

To pay: 19

total += price is shorthand for total = total + price. The other operators have one too: -=, *= and /=.

A loop can keep several of these at once, such as a count and a sum, each in its own variable made before the loop.