public Object summarize(int columnIndex) {
    int rowCount = dataProvider.getRowCount();
			
    float summaryValue = 0;

    for (int rowIndex = 0; rowIndex < rowCount; rowIndex++) {
        Object dataValue = dataProvider.getDataValue(columnIndex, rowIndex);

        if (dataValue instanceof Number) {
            summaryValue = summaryValue + Float.parseFloat(dataValue.toString());
        } else if (strict) {
            return DEFAULT_SUMMARY_VALUE;
        }
    }

    return summaryValue;
}