Reading X,Y,Z values from a G4ThreeVector

Hello,
This might be an elementary question but I have a G4ThreeVector PositionOfBall

How can I read x,y,z co-ordinates of PositionOfBall?
I tried PositionOfBall.GetX() and PositionOfBall.X() but neither of them worked.

G4ThreeVector is an alias to Hep3Vector from CLHEP, please see CLHEP/Vector/ThreeVector.h:

  inline double operator () (int) const;
  // Get components by index -- 0-based (Geant4)                                                                        

  inline double operator [] (int) const;
  // Get components by index -- 0-based (Geant4)                                                                        

  inline double & operator () (int);
  // Set components by index.  0-based.                                                                                 

  inline double & operator [] (int);
  // Set components by index.  0-based.                                                                                 

  inline double x() const;
  inline double y() const;
  inline double z() const;
  // The components in cartesian coordinate system.  Same as getX() etc.                                                

  inline void setX(double);
  inline void setY(double);
  inline void setZ(double);
  // Set the components in cartesian coordinate system.                                                                 

  inline void set( double x, double y, double z);
  // Set all three components in cartesian coordinate system.