code: public static void login(final String userId, final String password, final TokenChangedHandler tokenHandler) {
  		if (userId != null) {
  			logout();
  		}
  		loginOnly(userId, password, tokenHandler);
  	}
docs: Execute a login attempt, given a user name and password. If a user has already logged in, a logout will be called
  first.
  
  @param userId The unique user ID.
  @param password The user's password.
  @param tokenHandler actual handler whoch is used to change the token