Java Floating Point Number in Comma Instead of Dot

Java floating point number in comma instead of dot

When seeing your comment that the API accepts only Number and that it calls Number#toString() on it, then I see only 1 way to enforce the rightful display. By using your own implementation of Number and overwriting the way Object#toString() works:

public class CorrectlyDisplayedDouble extends Number{
private final Double internal;

public CorrectlyDisplayedDouble(Double internal){
this.internal = internal;

public int intValue(){
return internal.intValue();

public long longValue(){
return internal.longValue();

public float floatValue(){
return internal.floatValue();

public double doubleValue(){
return internal.doubleValue();

public String toString(){
// replaces periods with commas
return internal.toString().replace(".", ",");

Which can then be easily created using following snippet, which then also can be passed to your third party API:

Number number = new CorrectlyDisplayedDouble(Double.parseDouble(numberString));

How to set the floating point symbol in JSpinner to dot instead of comma if the locale is french?

I found the solution. When you use the method Locale.setDefault(Locale) it sets the default locale for display and also for formatting, but in my case, I need only to display my user interfaces in French. For that, I have to use also the second overload of the method : setDefault(Locale.Category, Locale), where the first parameter indicate if I want to use the locale for displaying user interfaces or for formatting date, numbers or curencies. The main method now is like this :

Locale.setDefault(Locale.FRENCH); // Display the user interfaces in French
Locale.setDefault(Locale.Category.FORMAT, Locale.ENGLISH); // But the formatting in English

NumberFormatException caused by a float having a comma instead of dot as decimal seperator

That seems likely to be related to running in a different Locale (such as Germany) where the decimal separator character is ','.

If you are actually parsing user input, you need to use a NumberFormat to parse the data.

Making doubles use commas instead of dots without importing formatting

Because you have said in your desired answer "123456789.0 needs to shown as 123,456,789" I am assuming you don't care about the single decimal place.

Wrap it with Decimal formatter:

DecimalFormat formatter = new DecimalFormat("###,###");

// Now wrap each and every desiredmethod output like formatter.format(methodOutput())
System.out.println("Name of dam:\t\t" + getName() +
"\nYear opened:\t\t" + getYear() +
"\nAge [yrs}:\t\t" + getAge() +
"\nDate as of:\t\t" + getDate() +
"\nStorage:\t\t" + getStorage() +
"\nCapacity:\t\t" + getCapacity() +
"\nInflow:\t\t\t" + formatter.format(getInflow()) +
"\nOutflow:\t\t" + formatter.format(getOutflow()) +
"\nStatus:\t\t\t" + getStatus() +
"\n%Full\t\t\t" + getPercentFull() + "%" +
"\nDays until dam event:\t" + getEventDays() +
"\nDate of event:\t\t" + getEventDate());

I didn't know which other ones you wanted, so only did for inFlow and outFlow. For reference - you can check

If you don't want to use Formatters, you can use plain String.format("%,.0f", yourDoubleValue)

Formatting doubles to two decimal places in Java produces a comma instead of a dot

If you want a dot rather than a comma, you should specify a Locale which uses dot as the decimal separator, e.g.

DecimalFormat df = new DecimalFormat("#.00",

Basically, "." in a format pattern doesn't mean "dot", it means "decimal separator".

format float[] to String decimal sign changes to comma

That is because String.format() is locale-aware. I'm guessing your default locale is Locale.GERMAN, since Locale.NORWEGIAN does not exist. And the decimal separator is a comma.

The locale always used is the one returned by Locale.getDefault().

If you want to format according to a specific locale, then you should use

Locale myLocale = ...;
String.format(myLocale, "%.2f", myNum[0]);

The Java Virtual Machine sets the default locale during startup based on the host environment. It is used by many locale-sensitive methods if no locale is explicitly specified. It can be changed using the setDefault method. You can easily check your locale: System.out.println(Locale.getDefault()).

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