code: public boolean addUserData(Object userData) {
  		if (this.userData == null) {
  			this.userData = new ArrayList<>();
  		}
  		return this.userData.add(userData);
  	}
docs: Add a user data in the data associated to this point.
  
  @param userData the user data to add.
  @return <code>true</code> if the data was added; otherwise <code>false</code>.