Abstract classes

public class zad_02 {
    public static void main(String[] args) {
        Triangle t = new Triangle(33, 55.66, 55.66);
        System.out.println("Triangle t perimeter: " + t.calcPerim() + " all sides equal: " + t.equalSides());

        Tetragon r = new Tetragon(77.77, 77.77, 77.77, 77.77);
        System.out.println("Rectangle r perimeter: " + r.calcPerim() + " all sides equal: " + r.equalSides());
    }
}

abstract class Shape {
    private double[] sides;
    public Shape(double ... a) {
        sides = a;
        /*
        sides = new double[a.length];
        for (int i = 0; i < a.length; i++) {
            sides[i] = a[i];
        }*/
    }
    public double[] getSides() {
        return sides;
    }
    public abstract double calcPerim();
    public abstract boolean equalSides();
}

class Triangle extends Shape {
    public Triangle(double a, double b, double c) {
        super(a, b, c);
    }
    public double calcPerim() {
        double A = getSides()[0];
        double B = getSides()[1];
        double C = getSides()[2];
        return A + B + C;
    }

    public boolean equalSides() {
        double temp = getSides()[0];
        for (int i = 1; i < getSides().length; i++) {
            if (temp != getSides()[i])
               return false;
        }
        return true;
    }
}

class Tetragon extends Shape {
    public Tetragon(double a, double b, double c, double d) {
        super(a, b, c, d);
    }
    public double calcPerim() {

        double temp = 0;
        for (int i = 0; i < getSides().length; i++)
            temp = temp + getSides()[i];
        return temp;
        /*
        double A = getSides()[0];
        double B = getSides()[1];
        double C = getSides()[2];
        double D = getSides()[3];
        return A + B + C + D;*/
    }

    public boolean equalSides() {
        double temp = getSides()[0];
        for (int i = 1; i < getSides().length; i++) {
            if (temp != getSides()[i])
                return false;
        }
        return true;
    }
}