import java.awt.Point;

public class Geom {

        public Point A;
        public Point B;
        public Point C;
        double AB = distance(A,B);
        double BC = distance(B,C);
        double AC = distance(A,C);

        Geom(Point A,Point B,Point C) {

            this.A = A;
            this.B = B;
            this.C = C;

        }
        public static double distance(Point M, Point N) {

            double dist = Math.sqrt((N.x - M.x)^2+(N.y - M.y)^2);
            return dist;

        }

        public double triangleSemiPerimeter() {

            double semi = (AC+AC+BC)/2;
            return semi;

        }
}

import java.awt.Point;


public class Password {

	public static void main(String[] args) {
            Point A = new Point(6,4);
            Point B = new Point(10,7);
            Point C = new Point(8,3);
            Geom myGeom = new Geom(A,B,C);

            System.out.print(myGeom.triangleSemiPerimeter());


        }

}


run:
Exception in thread "main" java.lang.NullPointerException
	at password.Geom.distance(Geom.java:23)
	at password.Geom.<init>(Geom.java:10)
	at password.Password.main(Password.java:12)
Java Result: 1
BUILD SUCCESSFUL (total time: 0 seconds)