Format negative amount of USD with a minus sign, not brackets (Java)

Here is one I always end up using either in a java class or via the fmt:formatNumber jstl tag:

DecimalFormat format = new DecimalFormat("$#,##0.00;$-#,##0.00");
String formatted = format.format(15.5);

It always produces at least a $0.00 and is consistent when displayed. Also includes thousands seperators where needed. You can move the minus sign in front of the dollar sign if that is your requirement.

It's probably best to create your own DecimalFormat if you want a specific format rather than relying on the default.

Edit: You could probably also cast the result of NumberFormat.getCurrencyInstance() to DecimalFormat and adjust it to your preferences.

Why poi REFUSES to support the FIRST option in excel currency formatting is beyond me!

I don't like using the DecimalFormat for currency because your end cell value becomes a non-numeric with the introduction of the currency symbol. While working for a major financial institution, I was tasked with resolving this formatting issue. The core idea of this change is, because POI refuses to be reasonable and have comprehensive support of Excel's native options, I will infiltrate their code and change their values at the core. The following is my WORKAROUND:

private static final String CURRENCY_FORMAT_OVERRIDE = "\"$\"#,##0.00_);-\"$\"#,##0.00";
private static final String CURRENCY_FORMAT_TARGET = "\"$\"#,##0.00_);(\"$\"#,##0.00)";    

static { // static class level initializer
    Field field = org.apache.poi.ss.usermodel.BuiltinFormats.class.getDeclaredField("_formats");            
    field.setAccessible(true);
    String[] _formats = (String[])field.get(new org.apache.poi.ss.usermodel.BuiltinFormats());
    for(int i = 0; i < _formats.length; ++i) {
        if(_formats[i].equals(CURRENCY_FORMAT_TARGET)) {
            _formats[i]=CURRENCY_FORMAT_OVERRIDE;
            System.out.println("TAKE THAT, POI!!!");
        }
    }
}