A DESCRIPTION OF THE PROBLEM :
Norwegian Nynorsk is a language in Norway: https://www.unicode.org/cldr/cldr-aux/charts/28/summary/nn.html and https://github.com/openjdk/jdk/blob/master/make/data/cldr/common/main/nn.xml
Formatting should be similar to Norwegian Bokmål https://github.com/openjdk/jdk/blob/master/make/data/cldr/common/main/nb.xml
In Java 17, 18 and 19 Norwegian Nynorsk defaults to English formatting when using BigDecimal, Integer and probably other types.

REGRESSION : Last worked in version 11.0.16.1

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
import java.math.BigDecimal;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.Locale;

public class JDKBug {

    public static void main(String args[]) {
        BigDecimal amount = new BigDecimal("2345.78");

        DecimalFormat norwegianNynorskAmountFormatter = getAmountFormatter(new Locale("nn", "NO"));
        System.out.println("Nynorsk amount formatting: " + norwegianNynorskAmountFormatter.format(amount));


        DecimalFormat norwegianBokmaalAmountFormatter = getAmountFormatter(new Locale("nb", "NO"));
        System.out.println("Bokmål amount formatting: " + norwegianBokmaalAmountFormatter.format(amount));
    }

    private static DecimalFormat getAmountFormatter(Locale locale) {
        NumberFormat nf = NumberFormat.getNumberInstance(locale);
        return (DecimalFormat) nf;
    }

}

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Nynorsk amount formatting: 2 345,78
Bokmål amount formatting: 2 345,78
ACTUAL -
Nynorsk amount formatting: 2,345.78
Bokmål amount formatting: 2 345,78

---------- BEGIN SOURCE ----------
See above source code
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CUSTOMER SUBMITTED WORKAROUND :
Use Norwegian Bokmål locale for formatting.

FREQUENCY : always