public class Mammal {
    protected int weight;
    public Mammal(int w) {
        weight = w;
    }
    public int getWeight() {
        return weight;
    }
    public boolean isSame(Mammal other) {
        System.out.println("In Mammal");
        return (this == other);
    }
}
public class Antelope extends Mammal {
    public Antelope(int w) { super(w); }
    public boolean isSame(Antelope other) {
        System.out.println("In Antelope");
        return ((other != null) && (this.weight == other.weight));
    }
}
public class Beaver extends Mammal {
    public Beaver(int w) { super(w); }
    public boolean isSame(Mammal other) {
        System.out.println("In Beaver");
        return ((other != null) && (other instanceof Beaver) && (this.weight == ((Beaver)other).weight));
    }
}

public class Program {
    public static void main(String[] args) {
        Antelope a1 = new Antelope(10);
        Object a2 = new Antelope(10);
        Beaver b1 = new Beaver(10);
        Mammal b2 = new Beaver(10);
        *******
    }
}