code: public boolean intersects(LineSegment lineSegment) {
  		double x1 = this.x1();
  		double y1 = this.y1();
  		double x2 = this.x2();
  		double y2 = this.y2();
  		double x3 = lineSegment.x1();
  		double y3 = lineSegment.y1();
  		double x4 = lineSegment.x2();
  		double y4 = lineSegment.y2();
  
  		double denom = (y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1);
  		if (denom == 0) {
  			return false;
  		}
  		double u1 = ((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / denom;
  		double u2 = ((x2 - x1) * (y1 - y3) - (y2 - y1) * (x1 - x3)) / denom;
  		return (u1 > 0 && u1 < 1 && u2 > 0 && u2 < 1);
  	}
docs: Does this linesegment intersect with another or not?
  
  @param lineSegment
  The other linesegment.
  @return Returns true if they intersect in 1 point, false otherwise.