Change DecimalFormat locale

You can specify locale for DecimalFormat this way:

DecimalFormatSymbols symbols = new DecimalFormatSymbols(Locale.US);
DecimalFormat format = new DecimalFormat("##.########", symbols);

You may try by first converting to NumberFormat and then Cast it to DecimalFormat

Integer vc = 3210000;
NumberFormat nf = NumberFormat.getNumberInstance(Locale.US);
DecimalFormat formatter = (DecimalFormat) nf;
formatter.applyPattern("#,###,###");
String fString = formatter.format(vc);
return convertNumbersToEnglish(fString);

You can use basic constructor for setting Locale while creating DecimalFormat object:

DecimalFormat dFormat = new DecimalFormat("#.#", new DecimalFormatSymbols(Locale.US));