Klasy macierzyste i potomne

package pl.am.object2.lesson27;

public class Kwadrat extends Prostokat {
    private double bok;

    public Kwadrat(double bok) {
        this.bok = bok;
    }

    public double obliczPole() {
        return this.bok*this.bok;
    }

    public double obliczObwod() {
        return 4* this.bok;
    }

    public double getBok() {
        return bok;
    }

    public void setBok(double bok) {
        this.bok = bok;
    }

    @Override
    public String toString() {
        return "Kwadrat{" +
                "bok=" + bok +
                ", pole=" + obliczPole() +
                ", obwód=" + obliczObwod() +
                '}';
    }
}

package pl.am.object2.lesson27;

public class Prostokat {
    private double a;
    private double b;

    public Prostokat() {
    }

    public Prostokat(double a, double b) {
        this.a = a;
        this.b = b;
    }

    public double getA() {
        return a;
    }

    public void setA(double a) {
        this.a = a;
    }

    public double getB() {
        return b;
    }

    public void setB(double b) {
        this.b = b;
    }

    public double obliczPole() {
        return this.a * this.b;
    }

    public double obliczObwod() {
        return 2*this.a + 2*this.b;
    }

    @Override
    public String toString() {
        return "Prostokat{" +
                "a=" + a +
                ", b=" + b +
                ", pole=" + obliczPole() +
                ", obwód=" + obliczObwod() +
                '}';
    }
}