Also see:

DecimalFormat

 public NumericCellRenderer() 
{
        super();
}

 public String getCellValue(WebTable table,
    Object data,
    int row,
    int col) 
{
        StringBuffer retVal = new StringBuffer(128);
        if (data == null) {
            return "";
        }
        if (data instanceof Number) {
            double cellValue = ((Number) data).doubleValue();
            if (cellValue  >= 0) {
                processNumber(retVal, _positiveColor, cellValue);
            } else {
                processNumber(retVal, _negativeColor, cellValue);
            }
            return retVal.toString();
        }
        return data.toString();
}

 protected  void processNumber(StringBuffer buf,
    String color,
    double cellValue) 
{
        if (color != null) {
            buf.append(" < font color='").append(color).append("' >");
        }
        buf.append(_formater.format(cellValue));
        if (color != null) {
            buf.append("< /font >");
        }
}

 public  void setFormatString(String format) 
{
        _formatString = format;
        _formater.applyPattern(_formatString);
}

 public  void setNegativeColor(String color) 
{
        _negativeColor = color;
}

 public  void setPositiveColor(String color) 
{
        _positiveColor = color;
}