判断空间上三个点是否共线问题【找bug篇】

判断空间上三个点是否在同一直线上【找bug篇】

作者：Vashon

时间：20150601 发布时间：20150718

一、拿到问题，首先分析并理清思路。

判断三点是否在同一条直线上需满足以下几点：

1、两点共点（p1与p2共点，p1与p3共点，p2与p3共点）

2、三点纵坐标相等，横坐标不相等

3、三点横坐标相等，且纵坐标不相等（横坐标不相等则不存在除数为0问题）

4、三点共点（可考虑可不考虑）

以上几点需要把斜率考虑在内（斜率相等（除数不能为0，且满足随机输入））

二、创建一个点的实体：

package com.ywx.entities;public class Point{private float x;private float y;public Point(float x,float y){this.x=x;this.y=y;}public float getX() {return x;}public void setX(float x) {this.x = x;}public float getY() {return y;}public void setY(float y) {this.y = y;}}

三、判断三点是否共线（包含历史测试代码）：

package com.ywx.isonlinetest;public class IsOnLine {public static boolean IsLine(Point p1,Point p2,Point p3){boolean flag=false;float k1=0.0f;//斜率float k2=0.0f;//斜率//1、两点共点（p1与p2共点，p1与p3共点，p2与p3共点）if((p1.getX()==p2.getX()&&p1.getY()==p2.getY())||(p1.getX()==p3.getX()&&p1.getY()==p3.getY())||(p2.getX()==p3.getX()&&p2.getY()==p3.getY())){flag=true;return flag;}//2、三点纵坐标相等，横坐标不相等if((p1.getY()==p2.getY())&&(p1.getY()==p3.getY())&&(p1.getX()!=p2.getX())&&(p1.getX()!=p3.getX())){flag=true;return flag;}//3、三点横坐标相等，且纵坐标不相等if((p1.getX()==p2.getX())&&(p1.getX()==p3.getX())&&(p1.getY()!=p2.getY())&&(p1.getY()!=p3.getY())){flag=true;return flag;}else{//横坐标不相等则不存在除数为0问题k1=(p3.getY()-p2.getY())/(p3.getX()-p2.getX());k2=(p1.getY()-p2.getY())/(p1.getX()-p2.getX());if(k1==k2){flag=true;return flag;}}//4、三点共点//if(p1.getX()==p2.getX()&&p1.getX()==p3.getX()//&&p1.getY()==p2.getY()&&p1.getY()==p3.getY()){//flag=true;//}//5、斜率相等（除数不能为0，且满足随机输入）//>>>>>中间点p2作为除数，，则可以随机输入//float n=p3.getX()-p2.getX();//float m=p1.getX()-p2.getX();//////if(n!=0&&m!=0){//除数不能为0//k1=(p3.getY()-p2.getY())/n;//k2=(p1.getY()-p2.getY())/m;//if(k1==k2){//flag=true;//}//}return flag;}//主方法@SuppressWarnings("static-access")public static void main(String args[]){//三点共点boolean bool=new IsOnLine().IsLine(new Point(0.0f,0.0f), new Point(0.0f,0.0f), new Point(0.0f,0.0f));// bool=new IsOnLine().IsLine(new Point(0.0f,0.0f), new Point(0.0f,0.0f), new Point(1.0f,1.0f));// bool=new IsOnLine().IsLine(new Point(1.0f,2.0f), new Point(2.0f,4.0f), new Point(4.0f,8.0f));// bool=new IsOnLine().IsLine(new Point(2.0f,3.0f), new Point(2.0f,5.0f), new Point(2.0f,8.0f)); bool=new IsOnLine().IsLine(new Point(1.0f,1.0f), new Point(1.0f,1.0f), new Point(1.0f,1.0f));//三点随机输入测试 bool=new IsOnLine().IsLine(new Point(0.0f,2.0f), new Point(1.0f,1.0f), new Point(2.0f,0.0f)); bool=new IsOnLine().IsLine(new Point(1.0f,1.0f), new Point(2.0f,0.0f), new Point(0.0f,2.0f)); bool=new IsOnLine().IsLine(new Point(2.0f,0.0f), new Point(0.0f,2.0f), new Point(1.0f,1.0f));System.out.println("三点是否共线:"+bool);}}四、用Junit测试（此部分主要是学习Junit测试）：package com.ywx.test;import org.junit.After;import org.junit.Assert;import org.junit.Before;import org.junit.BeforeClass;import org.junit.Ignore;import org.junit.Test;import com.ywx.count.IsOnLine;import com.ywx.count.Point;@SuppressWarnings("static-access")public class IsOnLineTest{@Testpublic void test1(){//测试三点在原点（或共点）boolean bool=new IsOnLine().IsLine(new Point(0.0f,0.0f),new Point(0.0f,0.0f),new Point(0.0f,0.0f));bool=new IsOnLine().IsLine(new Point(3.0f,3.0f),new Point(3.0f,3.0f),new Point(3.0f,3.0f));System.out.println("三点是否共线："+bool);}@Testpublic void test2(){//三点随机输入boolean bool=new IsOnLine().IsLine(new Point(0.0f,2.0f), new Point(1.0f,1.0f), new Point(2.0f,0.0f));bool=new IsOnLine().IsLine(new Point(1.0f,1.0f), new Point(2.0f,0.0f), new Point(0.0f,2.0f));bool=new IsOnLine().IsLine(new Point(2.0f,0.0f), new Point(0.0f,2.0f), new Point(1.0f,1.0f));System.out.println("三点是否共线："+bool);}@Testpublic void test3(){//横坐标相等boolean bool=new IsOnLine().IsLine(new Point(1.0f,2.0f), new Point(1.0f,2.0f), new Point(1.0f,5.0f));System.out.println("三点是否共线："+bool);}@Testpublic void test4(){//纵坐标相等boolean bool=new IsOnLine().IsLine(new Point(5.0f,2.0f), new Point(1.0f,2.0f), new Point(3.0f,2.0f));System.out.println("三点是否共线："+bool);}@Testpublic void test5(){//斜率测试1boolean bool=new IsOnLine().IsLine(new Point(1.0f,2.0f),new Point(2.0f,4.0f),new Point(3.0f,6.0f));bool=new IsOnLine().IsLine(new Point(0.0f,-1.0f),new Point(1.0f,0.0f),new Point(2.0f,1.0f));System.out.println("三点是否共线："+bool);}@Testpublic void test6(){//斜率测试2boolean bool=new IsOnLine().IsLine(new Point(0.0f,-1.0f),new Point(1.0f,0.0f),new Point(2.0f,1.0f));bool=new IsOnLine().IsLine(new Point(1.0f,0.0f),new Point(2.0f,1.0f),new Point(0.0f,-1.0f));bool=new IsOnLine().IsLine(new Point(2.0f,1.0f),new Point(0.0f,-1.0f),new Point(1.0f,0.0f));System.out.println("三点是否共线："+bool);}@Testpublic void test7(){boolean bool=false;Assert.assertTrue("返回结果：", new IsOnLine().IsLine(new Point(0.0f,-1.0f),new Point(1.0f,0.0f),new Point(2.0f,1.0f)));Assert.assertTrue("返回结果：", new IsOnLine().IsLine(new Point(0.0f,-1.0f),new Point(1.0f,0.0f),new Point(2.0f,1.0f)));Assert.assertTrue("返回结果：", new IsOnLine().IsLine(new Point(0.0f,-1.0f),new Point(1.0f,0.0f),new Point(2.0f,1.0f)));}@Testpublic void test0(){Assert.assertTrue("返回结果：", new IsOnLine().IsLine(new Point(1.0f,0.0f),new Point(2.0f,0.0f),new Point(3.0f,0.0f)));Assert.assertTrue("返回结果：", new IsOnLine().IsLine(new Point(0.0f,1.0f),new Point(0.0f,2.0f),new Point(0.0f,3.0f)));}@Beforepublic void test8(){System.out.println("开始测试。。。");}@Afterpublic void test9(){System.out.println("测试结束。。。");}}

后记：最后得感谢当时带我的在一线打拼十余年的技术大牛，虽然这是一个小程序，但在他的苛刻要求及耐心指引下意识到很多，这将会在我以后的工作中能派上用场。

总结：小小事情，大感悟。

即将转出来的那一面，是快乐或痛苦，是爱还是恨。

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