来问一下JAVA中类的问题

public class Box {
    private static int length;
    private static int width;
    private static int height;

    public static void set(int l, int w, int h){
        Box.length = l;
        Box.width = w;
        Box.height = h;
    }
    public static void volume(){
        System.out.println(Box.length*Box.width*Box.height);
    }
    public static void main(String[] args) {
        set(1,2,3);
        volume();
    }
}

emmm

你这是一点不会呢