School, 19.09.2017, Point and Triangle

Point class
=============

public class Point {
    private String name;
    private double x;
    private double y;

    public Point(String name, double x, double y) {
        this.name = name;
        this.x = x;
        this.y = y;
    }

    public Point(Point p) {
        this.name = p.name;
        this.x = p.x;
        this.y = p.y;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getX() {
        return x;
    }

    public void setX(double x) {
        this.x = x;
    }

    public double getY() {
        return y;
    }

    public void setY(double y) {
        this.y = y;
    }

    public double distanceTo(Point p) {
        double dx = this.x - p.x;
        double dy = this.y - p.y;

        double d = Math.sqrt(dx * dx + dy * dy);

        return d;
    }

    @Override
    public String toString() {
        return "Point [name=" + name + ", x=" + x + ", y=" + y + "]";
    }
}


Triangle class
===============
import java.util.Arrays;

public class Triangle {
    private Point[] points;

    public Triangle(Point[] points) {
        this.points = points;
    }

    public Triangle(Point p1, Point p2, Point p3) {
        this.points = new Point[3];
        this.points[0] = new Point(p1);
        this.points[1] = new Point(p2);
        this.points[2] = new Point(p3);
    }

    public Point[] getPoints() {
        return points;
    }

    public Point getPoint(int i) {
        // i is 1 or 2 or 3
        return this.points[i - 1];
    }

    public void setPoint(int i, Point point) {
        // i is 1 or 2 or 3
        this.points[i - 1] = new Point(point);
    }

    public double getPerimeter() {
        // not a good way
        double l1 = points[0].distanceTo(points[1]);
        double l2 = points[1].distanceTo(points[2]);
        double l3 = points[2].distanceTo(points[0]);

        return l1 + l2 + l3;
    }

    public double getArea() {
        double l1 = points[0].distanceTo(points[1]);
        double l2 = points[1].distanceTo(points[2]);
        double l3 = points[2].distanceTo(points[0]);

        double s = (l1 + l2 + l3) / 2;

        return Math.sqrt(s * (s - l1) * (s - l2) * (s - l3));
    }

    @Override
    public String toString() {
        return "Triangle [points=" + Arrays.toString(points) + "]";
    }

}

Tester class
==============

public class Tester {

    public static void main(String[] args) {
        Point p1 = new Point("Aa", 0, 3);
        Point p2 = new Point("Ax", 0, 0);
        Point p3 = new Point("Ag", 4, 0);

        Triangle t1 = new Triangle(p1, p2, p3);

        System.out.println(t1);
        System.out.println(t1.getPerimeter());
        System.out.println(t1.getArea());

        t1.setPoint(1, new Point("D", 3, 6));

        t1.getPoint(2).setX(4);
        t1.getPoint(2).setY(8);

        t1.setPoint(3, new Point("E", 5, 15));
        System.out.println(t1);
        System.out.println(t1.getPerimeter());
        System.out.println(t1.getArea());
    }

}