code: public void error( String format, Object arg1, Object arg2 )
      {
          if( m_delegate.isErrorEnabled() )
          {
              FormattingTuple tuple = MessageFormatter.format( format, arg1, arg2 );
              m_delegate.error( tuple.getMessage(), tuple.getThrowable() );
          }
      }
docs: Log a message at the ERROR level according to the specified format
  and arguments.
  
  <p>This form avoids superfluous object creation when the logger
  is disabled for the ERROR level. </p>
  
  @param format the format string
  @param arg1   the first argument
  @param arg2   the second argument