public function swapRows( $row1, $row2 )
	{
		if( $row1 < 0 || $row1 >= $this->getRowNumber() )
			throw new OutOfRangeException( 'Source Row key "'.$row1.'" is not valid.' );
		if( $row2 < 0 || $row2 >= $this->getRowNumber() )
			throw new OutOfRangeException( 'Target Row key "'.$row2.'" is not valid.' );

		$buffer	= $this->values[$row2];
		$this->values[$row2]	= $this->values[$row1];
		$this->values[$row1]	= $buffer;
	}