public class Triangle {
   Point a;
   Point b;
   Point c;
   public Triangle(Point a, Point b, Point c) {
       this.a = a;
       this.b = b;
       this.c = c;
   }
   public String toString() {
       return "Dreieck mit den Punkten: " + a + ", " + b + ", " + c;
   }
   public double perimeter(Triangle t) {
       double u = a.distance(b) + b.distance(c) + c.distance(a);
       return u;
   }
   public static void main(String[] args) {
       Point p1 = new Point(1, 1);
       Point p2 = new Point(2, 2);
       Point p3 = new Point(1, 3);
       Triangle t1 = new Triangle(p1, p2, p3);
       System.out.println(t1);
       System.out.println(t1.perimeter());
   }
}