How to change the decimal separator of DecimalForm

问题:

I have this little crazy method that converts BigDecimal values into nice and readable Strings.

private String formatBigDecimal(BigDecimal bd){
    DecimalFormat df = new DecimalFormat();
    df.setMinimumFractionDigits(3);
    df.setMaximumFractionDigits(3);
    df.setMinimumIntegerDigits(1);
    df.setMaximumIntegerDigits(3);
    df.setGroupingSize(20);
    return df.format(bd);
}

It however, also produces a so called grouping separator \",\" that makes all my values come out like this:

xxx,xxx

I do need the separator to be a dot or a point and not a comma. Does anybody have a clue of how to accomplish this little feat?

I have read this and in particular this to death now but I cannot find a way to get this done. Am I approaching this the wrong way? Is there a much more elegant way of doing this? Maybe even a solution that accounts for different local number representations, since the comma would be perfect by European standards.

回答1:

You can change the separator either by setting a locale or using the DecimalFormatSymbols.

If you want the grouping separator to be a point, you can use an european locale:

NumberFormat nf = NumberFormat.getNumberInstance(Locale.GERMAN);
DecimalFormat df = (DecimalFormat)nf;

Alternatively you can use the DecimalFormatSymbols class to change the symbols that appear in the formatted numbers produced by the format method. These symbols include the decimal separator, the grouping separator, the minus sign, and the percent sign, among others:

DecimalFormatSymbols otherSymbols = new DecimalFormatSymbols(currentLocale);
otherSymbols.setDecimalSeparator(\',\');
otherSymbols.setGroupingSeparator(\'.\'); 
DecimalFormat df = new DecimalFormat(formatString, otherSymbols);

currentLocale can be obtained from Locale.getDefault() i.e.:

Locale currentLocale = Locale.getDefault();

回答2:

Europe is quite huge. I\'m not sure if they use the same format all over. However this or this answer will be of help.

String text = \"1,234567\";
NumberFormat nf_in = NumberFormat.getNumberInstance(Locale.GERMANY);
double val = nf_in.parse(text).doubleValue();

NumberFormat nf_out = NumberFormat.getNumberInstance(Locale.UK);
nf_out.setMaximumFractionDigits(3);
String output = nf_out.format(val);

I.e. use the correct locale.

回答3:

public String getGermanCurrencyFormat(double value) {
    NumberFormat nf = NumberFormat.getNumberInstance(Locale.GERMAN);
    nf.setGroupingUsed(true);
    return \"€ \" + nf.format(value);
}

回答4:

BigDecimal does not seem to respect Locale settings.

Locale.getDefault(); //returns sl_SI

Slovenian locale should have a decimal comma. Guess I had strange misconceptions regarding numbers.

a = new BigDecimal(\"1,2\") //throws exception
a = new BigDecimal(\"1.2\") //is ok

a.toPlainString() // returns \"1.2\" always

I have edited a part of my message that made no sense since it proved to be due the human error (forgot to commit data and was looking at the wrong thing).

Same as BigDecimal can be said for any Java .toString() functions. I guess that is good in some ways. Serialization for example or debugging. There is an unique string representation.

Also as others mentioned using formatters works OK. Just use formatters, same for the JSF frontend, formatters do the job properly and are aware of the locale.

回答5:

String money = output.replace(\',\', \'.\');

回答6:

Just replace \'.\' with \',\' in the UI end

import java.text.DecimalFormat;
public MyClass{
    private String netAmount;
    private static DecimalFormat twoDecimalForm = new DecimalFormat(\"00.00\");

    public MyClass(double amount){
        //converting to required decimal format in constructor or/and setter
        this.amount=twoDecimalForm.format(amount);
    }

    public String getAmount() {
        //replacing decimal point with  comma so that in JSP ELs you\'ll get it in comma format
        return amount.replace(\".\",\",\");
    }
    public void setAmount(String amount) {
        this.amount = amount;
    }
}