BODMAS, Java. Simple Math that won't Add Up

Question

Hello can't figure out why I can't get right result for startE

just a simple program, to illustrate the problem.

"NUMBER CLASS"

public class Number {

    public static void main(String[] args) {
        Grow big = new Grow();
        big.growing();
    }}

"GROW CLASS"

public class Grow {
    private int startE = 50000 / 1 / 2;
    private int startC = 50000 / 1 / 3;

    public void growing() {

        for (int i = 0; i < 10; i++) {

            startE = startE + (((50000 * (13 / 20)) - (50000 * (1 / 2))) / 200);
            startC = startC + ((50000 / 1 / 2 - 50000 / 1 / 3) / 75);

            System.out.println(startE);
            System.out.println(startC);

        }
    }}

You will see that 'startC' does as expected, however I am getting no joy with 'startE' If you can help that would be great

What it prints out on console.

25000
25000
25000
25000
25000 etc

Answer 1

You have this problem because of how integer division works in Java:

startE = startE + (((50000 * (13 / 20)) - (50000 * (1 / 2))) / 200);

When you do 13/20 above, it returns 0 because all the values following the decimal point are discarded in ints. This is equivalent of the floor in math. When you multiply 50000 with 0, you get a 0. Same thing with 1/2. It becomes 0 and 0 multiplied by anything is 0.

Your startE value starts at 25000. When you add 0 to 25000 you get 25000. That is the reason you keep seeing 25000 in the loop.