JAVA学习日报 8.4

今天咱们来判断三角形，这也是暑假程序设计技能实训的作业之一

由于double类型的精度和sqrt()方法本身的问题，实际开方的结果与真实结果有那么一丢丢误差，解决这种误差可以通过近似取值方法来解决

代码如下：

package test2;
import java.lang.Math;
import java.util.Scanner;
class point
{
    public double x=0;
    public double y=0;
    public point(double x1,double y1){
        this.x=x1;this.y=y1;
    }
}
class Triangle
{
    private double d=0,e=0,f=0;
    public Triangle() {}
    public Triangle(double a,double b,double c){
              this.d=a;this.e=b;this.f=c;
         }
        void settri(point a,point b,point c)
        {
            d=Math.sqrt(((a.x-b.x)*(a.x-b.x))+((a.y-b.y)*(a.y-b.y)));
            e=Math.sqrt(((c.x-b.x)*(c.x-b.x))+((c.y-b.y)*(c.y-b.y)));
            f=Math.sqrt(((a.x-c.x)*(a.x-c.x))+((a.y-c.y)*(a.y-c.y)));
        }
        double fabs(double x){
            if(x<=0)
                return x;
            else
                return 0-x;
        }
        void checkitout()
        {
            int g=0,zj=0,dy=0,db=0;
            if(d+e<f||f+e<d||d+f<e)
            {System.out.print("这三个点不能构成三角形\n");}
            else
            {
                System.out.print("这三个点可以构成三角形\n");
                g=1;
            }
            if(g==1)
            {
                if(fabs((f*f)+(d*d)-(e*e))<=0.001||fabs((f*f)-(d*d)+(e*e))<0.001||fabs((f*f)+(d*d)-(e*e))<0.001)
                {zj=1;}
                if(d==e||f==e||d==f) 
                {dy=1;}
                if(e==d&&e==f)
                {db=1;}
                if(db==1) 
                {System.out.print("为等边三角形\n");}
                else if(dy==1)
                {
                    if(zj==1)
                    {System.out.print("为等腰直角三角形\n");}
                    else
                    {System.out.print("为等腰三角形\n");}
                }
                else if(zj==1)
                {System.out.print("为直角三角形\n");}
                if(db==0&&zj==0&&dy==0)
                {
                    System.out.print("这是一个普通三角形\n");
                }
            }
        }
};
public class Class12 {

    public static void main(String[] args) {
        Triangle t=new Triangle();
        double a,b;
        Scanner input=new Scanner(System.in);
        System.out.print("输入三个点\n");
        System.out.print("x1:");a=input.nextDouble();
        System.out.print("y1:");b=input.nextDouble();
        point p1=new point(a,b);
        System.out.print("x2:");a=input.nextDouble();  
        System.out.print("y2:");b=input.nextDouble();
        point p2=new point(a,b);
        System.out.print("x3:");a=input.nextDouble();
        System.out.print("y3:");b=input.nextDouble();
        point p3=new point(a,b);
        t.settri(p1,p2,p3);
        t.checkitout();
        input.close();
    }

}

运行结果如下：