Основы ООП в языке Java

final class Point {
    private final double x;
    private final double y;
 
    public Point(double x, double y) {
        this.x = x;
        this.y = y;
    }
 
    public double getX() {
        return x;
    }
 
    public double getY() {
        return y;
    }
 
    public double getDistanceTo(Point other) {
        return Math.sqrt(Math.pow(getX() - other.getX(), 2.0) +
            Math.pow(getY() - other.getY(), 2.0));
    }
 
    @Override
    public String toString() {
        return "Point{" +
                "x=" + x +
                ", y=" + y +
                '}';
    }
}
 
final class Rectangle {
    private final Point topLeft;
    private final Point topRight;
    private final Point bottomRight;
    private final Point bottomLeft;
 
    // precomputed values
    private final double sideTop;
    private final double sideRight;
    private final double sideBottom;
    private final double sideLeft;
    private final double mainDiagonal;
    private final double minorDiagonal;
    private final double perimeter;
    private final double area;
 
    public Rectangle(Point topLeft, Point topRight, Point bottomRight, Point bottomLeft) {
        this.topLeft = topLeft;
        this.topRight = topRight;
        this.bottomRight = bottomRight;
        this.bottomLeft = bottomLeft;
        this.sideTop = topLeft.getDistanceTo(topRight);
        this.sideRight = topRight.getDistanceTo(bottomRight);
        this.sideBottom = bottomRight.getDistanceTo(bottomLeft);
        this.sideLeft = topLeft.getDistanceTo(bottomLeft);
        this.mainDiagonal = topLeft.getDistanceTo(bottomRight);
        this.minorDiagonal = bottomLeft.getDistanceTo(topRight);
        this.perimeter = this.sideTop + this.sideRight + this.sideBottom + this.sideLeft;
        final double k = 4 * Math.pow(this.mainDiagonal, 2.0) * Math.pow(this.minorDiagonal, 2.0);
        final double d = Math.pow(Math.pow(this.sideRight, 2.0) + Math.pow(this.sideLeft, 2.0) -
                Math.pow(this.sideTop, 2.0) - Math.pow(this.sideBottom, 2.0), 2.0);
        this.area = Math.sqrt(k - d) / 4;
    }
 
    public Point getTopLeft() {
        return topLeft;
    }
 
    public Point getTopRight() {
        return topRight;
    }
 
    public Point getBottomRight() {
        return bottomRight;
    }
 
    public Point getBottomLeft() {
        return bottomLeft;
    }
 
    public double getPerimeter() {
        return perimeter;
    }
 
    public double getMainDiagonal() {
        return mainDiagonal;
    }
 
    public double getMinorDiagonal() {
        return minorDiagonal;
    }
 
    public double getSideTop() {
        return sideTop;
    }
 
    public double getSideRight() {
        return sideRight;
    }
 
    public double getSideBottom() {
        return sideBottom;
    }
 
    public double getSideLeft() {
        return sideLeft;
    }
 
    public double getArea() {
        return area;
    }
 
    @Override
    public String toString() {
        return "Rectangle{" +
                "topLeft=" + topLeft +
                ", topRight=" + topRight +
                ", bottomRight=" + bottomRight +
                ", bottomLeft=" + bottomLeft +
                ", sideTop=" + sideTop +
                ", sideRight=" + sideRight +
                ", sideBottom=" + sideBottom +
                ", sideLeft=" + sideLeft +
                ", mainDiagonal=" + mainDiagonal +
                ", minorDiagonal=" + minorDiagonal +
                ", perimeter=" + perimeter +
                ", area=" + area +
                '}';
    }
}
 
public class Launcher {
    public static void main(String[] args) {
        System.out.println(new Rectangle(new Point(0, 1), new Point(1, 1),
                new Point(1, 0), new Point(0, 0)));
 
    }
}