public LineSegment transformBy(Matrix m){
  Vector newStart=startPoint.cross(m);
  Vector newEnd=endPoint.cross(m);
  return new LineSegment(newStart,newEnd);
}

public LineSegment transformBy ( Matrix m ) { Vector newStart = startPoint . cross ( m ) ; Vector newEnd = endPoint . cross ( m ) ; return new LineSegment ( newStart , newEnd ) ; }
transforms the segment by the specified matrix
