private double get2PointDirectionAngle(long x1, long y1, long x2, long y2){
		long dx = x2-x1;
		long dy = y2-y1;
		double m = (double)dy/(double)dx;
		if (dx > 0 && dy > 0){
			return Math.atan(m);
		}else if(dx<0 && dy>0){
			return 180 + Math.atan(m);
		}else if(dx<0 && dy<0){
			return 180 +Math.atan(m);
		}else if(dx>0 && dy<0){
			return 360 +Math.atan(m);
		}
		return 0;
	}