public function setExtensions( $extensions = array() )
	{
		if( !is_array( $extensions ) )
			throw new InvalidArgumentException( 'Extensions must be given as Array.' );

		$pattern	= "";
		if( count( $extensions ) )
		{
			$extensions	= implode( "|", array_values( $extensions ) );
			$pattern	= '@\.'.$extensions.'$@i';
		}
		$this->pattern	= $pattern;
	}