code: public void setParent(Logger parent) {
          if (parent == null) {
              throw new NullPointerException();
          }
          manager.checkPermission();
          doSetParent(parent);
      }
docs: Set the parent for this Logger.  This method is used by
  the LogManager to update a Logger when the namespace changes.
  <p>
  It should not be called from application code.
  <p>
  @param  parent   the new parent logger
  @exception  SecurityException  if a security manager exists and if
  the caller does not have LoggingPermission("control").