triangle.java

输入三角形的三点坐标

class Triangle{

   Point p1,p2,p3;
   float s1,s2,s3;
   float per;
   float area;

   public Triangle(){
	   System.out.println("the first point(x1,y1): ");
	   p1 = new Point();
	   System.out.println("the second point(x2,y2): ");
	   p2 = new Point();
	   System.out.println("the third point(x3,y3): ");
	   p3 = new Point();
	   }

   public float side(Point a,Point b){
	   float n = a.x - b.x;
	   float m = a.y - b.y;
	   float s =(float)Math.sqrt( n*n + m*m );
	   return s;
       }

   public boolean check(Point p1 ,Point p2 ,Point p3){
    if(p1.x==p2.x && p1.y==p2.y){System.out.println("Error");return false;}
    else if(p1.x==p3.x && p1.y==p3.y){System.out.println("Error");return false;}
    else if(p3.x==p2.x && p3.y==p2.y){System.out.println("Error");return false;}
    else if((p1.x==p2.x&&p2.x==p3.x)||(p1.y==p2.y&&p2.y==p3.y)){System.out.println("Error");return false;}
    else return true;
}

   public void permimeter(float s1,float s2,float s3){
     per = s1+s2+s3;
   }

   public void area(Point p1,Point p2,Point p3){
     float r,r1,r2,r3;
     float max,min;
     float c,k;
     if(p1.x<=p2.x && p1.x<=p3.x)min=p1.x;
     if(p2.x<=p3.x && p2.x<=p1.x)min=p2.x;
     else min =p3.x;

     if(p1.x>=p2.x && p1.x>=p3.x)max=p1.x;
	 if(p2.x>=p3.x && p2.x>=p1.x)max=p2.x;
     else max=p3.x;

     c=max-min;

    if(p1.y<=p2.y && p1.y<=p3.y)min=p1.y;
	if(p2.y<=p3.y && p2.y<=p1.y)min=p2.y;
	else min =p3.y;

	if(p1.y>=p2.y && p1.y>=p3.y)max=p1.y;
	if(p2.y>=p3.y && p2.y>=p1.y)max=p2.y;
	else max=p3.y;

    k=max-min;

    r=c*k;
     r1 =Math.abs(p1.x-p2.x)*Math.abs(p1.y-p2.y)/2;
     r2 =Math.abs(p1.x-p3.x)*Math.abs(p1.y-p3.y)/2;
     r3 =Math.abs(p3.x-p2.x)*Math.abs(p3.y-p2.y)/2;
     area = r-r1-r2-r3;

   }

 public static void main(String arg[]){
       Triangle t = new Triangle();
       t.check(t.p1,t.p2,t.p3);
    if(t.check(t.p1,t.p2,t.p3)){
       t.s1 = t.side(t.p1,t.p2);
       t.s2 = t.side(t.p1,t.p3);
       t.s3 = t.side(t.p2,t.p3);
       t.permimeter(t.s1,t.s2,t.s3);
       t.area(t.p1,t.p2,t.p3);
       System.out.println("the permeter is :"+t.per);
       System.out.println("the area is :"+t.area);
      }
    }
}