How to change the decimal separator of DecimalFormat from comma to dot/point?

Question

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();

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.

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

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.

This worked in my case:

DecimalFormat df2 = new DecimalFormat("#.##");           
df2.setDecimalFormatSymbols(DecimalFormatSymbols.getInstance(Locale.ENGLISH));

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