public interface Venomous {
    boolean isVenomous();
}

public class Anfibio implements  Venomous {
    private boolean isVenomous;

    public boolean isVenomous() {
        return isVenomous;
    }
}

public class Cobra implements  Venomous {
    private boolean isVenomous;

    public boolean isVenomous() {
        return isVenomous;
    }
}

public int howManyVenomous(List<Venomous> venenosos) {
    int sum = 0;

    for(int i  = 0; i < venenosos.size(); i++ {
        if (venenosos[i].isVenomous) {
            sum++;
        }
    }
    return sum;
}