I've got no idea what this specific part means : I've got this code and i've got the answer for it as well, but I don't understand how they come out like that, specifically what does (x+" "+y) part means as well as the changeUs(x, y), can anyone explain?

    public class ChangeParam {

	public static void main(String[] args) {
		int x = 1;
		double y = 3.4;
		System.out.println(x+" "+y);
		changeUs(x, y);
        System.out.println(x+" "+y);		
	}
	
	public static void changeUs(int x, double y) {
		x = 0;
		y = 0.0;
		System.out.println(x +" "+y);
	}

}


the answers are: 

1 3.4

0 0.0

1 3.4