Different between divide by int, and divide by double

DivideExample.java

public class DivideExample {
    public static void main(String[] args) {
        int a = 9;
        int b = 2;
        int c = 5;
        double average1 =  (a+b+c) / 3;
        System.out.println("average1 of a+b+c = " + average1);

        int x = 9;
        int y = 2;
        int z = 5;
        double average2 =  (x+y+z) / 3.0;
        System.out.println("average2 of x+y+z = " + average2);
    }
}