Question

In a web application ,I want to model an ItemForSale which has a price field.I read elsewhere that float or double should not be used for currency fields due to rounding errors and BigDecimal is the proper type for this purpose.I created these classes

class ItemForSale {
    private String name;
    private BigDecimal price;
    ...
}

class MyUtils{
    ...
    public static BigDecimal parsePriceOfItem(String priceStr){
        BigDecimal price;
        BigDecimal zero = new BigDecimal(0);
        try{
            price = new BigDecimal(priceStr);
        }catch(NumberFormatException nfe){
            price = zero;
        }
        if(price.doubleValue() < zero.doubleValue()){
            price = zero;
        }
        return price;
        }
    }

Is this the right way to parse a price string(as entered by user)?I wanted to treat negative and invalid strings (say ‘abcd’) as 0.

If there is a better way ,please tell me

thanks

mark

Answer 1

Why would you want to treat invalid input as 0? Surely you’d want to tell the user that they’ve made a mistake, rather than treating it as if they’d typed in zero.

If you’re parsing user input, you should probably be using DecimalFormat instead of the BigDecimal constructor – that way it will use the appropriate cultural information. (Use setParseBigDecimal to make DecimalFormat parse to BigDecimal instead of double.)

Then instead of converting the BigDecimal values to doubles, use:

if (price.compareTo(BigDecimal.ZERO) < 0)

I would suggest that you should indicate to the user three different states:

• Number can’t be parsed
• Number was negative (or possibly invalid in some other way; do you have a maximum value, or a maximum number of digits)?
• Number was valid