Java messing around, Java

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// A complete implementation of Box Weight.
class Box {
    private double width;
    private double height;
    private double depth;
    // construct clone of an object
    Box(Box ob) { // Pass object to constructor
        width = ob.width;
        height = ob.height;
        depth = ob.depth;
    }
    
    // constructor used when all dimensions specified 
    Box(double w, double h, double d) {
        width = w;
        height = h;
        depth = d;
    }
    
    // constructor used when no dimensions are specified
    Box() {
   width = -1; // use -1 to indicate
        height = -1; // an unintialized
        depth = -1; // box
    }
    
    // constructor used when cube is created
    Box(double len) {
        width = height = depth = len;
    }
    
    // compute and return volume
    double volume() {
        return width * height * depth;
    }
}

// BoxWeight now fully implements all constructors
class BoxWeight extends Box {
    double weight; // weight of box

// construct clone of an object 
    BoxWeight(BoxWeight ob) { // pass object to constructor
        super(ob);
    }
    
   
    // constructor when all parameters are specified
    BoxWeight(double w, double h, double d, double m) {
        super(w, h, d); // call superclass constructor
        weight = m;
    }
    
    // default constructor
    BoxWeight() {
        super();
        weight = -1;
    }
    
    // constructor used when cube is created
    BoxWeight(double len, double m) {
        super(len);
        weight = m;
    }
}

class DemoSuper {
    public static void main (String args[])
        BoxWeight mybox1 = new BoxWeight (10, 20, 15, 34.3);
    BoxWeight mybox2 = new BoxWeight (2, 3, 4, 0.076);
    BoxWeight mybox3 = new BoxWeight(); // default
        BoxWeight mycube = new BoxWeight (3, 2);
        BoxWeight myclone = new BoxWeight (mybox1);
        double vol;

vol = mybox1.volume(); 
    System.out.printin("Volume of mybox is " + vol);
        System.out.printin("Weight of mybox1") + mybox1.weight);
        System.out.printin();

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Compilation time: 0.42 sec, absolute service time: 0,58 sec