package com.cs.ff;
import java.awt.geom.Point2D;


public class Z1 {

    // 两点之间的距离

    public static double distanceOfPoints(Point2D p1, Point2D p2) {

        double disX = p2.getX() - p1.getX();

        double disY = p2.getY() - p1.getY();

        double dis = Math.sqrt(disX * disX + disY * disY);


        return dis;

    }


    // 两点的中点

    public static Point2D middlePoint(Point2D p1, Point2D p2) {

        double x = (p1.getX() + p2.getX()) / 2;

        double y = (p1.getY() + p2.getY()) / 2;


        return new Point2D.Double(x, y);

    }


    // 在两点所在直线上，以从startPoint到endPoint为方向，离startPoint的距离disToStartPoint的点

    public static Point2D extentPoint(Point2D startPoint, Point2D endPoint, double disToStartPoint) {

        double disX = endPoint.getX() - startPoint.getX();

        double disY = endPoint.getY() - startPoint.getY();

        double dis = Math.sqrt(disX * disX + disY * disY);

        double sin = (endPoint.getY() - startPoint.getY()) / dis;

        double cos = (endPoint.getX() - startPoint.getX()) / dis;

        double deltaX = disToStartPoint * cos;

        double deltaY = disToStartPoint * sin;


        return new Point2D.Double(startPoint.getX() + deltaX, startPoint.getY() + deltaY);

    }

}