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{
	
	@Test
	public 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);
	}
	@Test
	public 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);
	}
	@Test
	public 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);
	}
	@Test
	public 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);
	}
	@Test
	public void test5(){//斜率测试1
		boolean 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);
	}
	@Test
	public void test6(){//斜率测试2

		boolean 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);
	}
	@Test
	public 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)));
	}
	
	
	@Test
	public 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)));
		
		
	}
	@Before
	public void test8(){
		System.out.println("开始测试。。。");
	}
	@After
	public 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。

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