A swap method that does not swap

class Box {
    int value;

    Box(int value) {
        this.value = value;
    }
}

public class Main {
    static void swap(Box p, Box q) {
        Box t = p;
        p = q;
        q = t;
    }

    static void swapValues(Box p, Box q) {
        int t = p.value;
        p.value = q.value;
        q.value = t;
    }

    public static void main(String[] args) {
        Box a = new Box(1);
        Box b = new Box(2);
        swap(a, b);
        System.out.println(a.value + " " + b.value);
        swapValues(a, b);
        System.out.println(a.value + " " + b.value);
    }
}