Java String.format()

I have a string and I want to format it in a custom way.
This is my String:

String amount = "355128000";

I want it to be formatted like this way:

String formattedAMount = "3 551 280,00"

With a space after first number and a group of 3 numbers and a comma at the end before two nubmers

You can format it with String.format() if you first convert it to `double':

String amount = "355128000";
double amountDouble = Double.parseDouble(amount);

String formattedAmount = String.format("%,.2f", amountDouble);
// 355,128,000.00

if you want to look it exactly like as you showed you can achieve this by:

String formattedAmount = String.format("%,.2f", amountDouble).replace(",", " ").replace(".", ",");

But String.format() might not be the best way for this purpose, use DecimalFormat instead.

You can create an instance of NumberFormatter and specify options:

import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.text.NumberFormat;
import java.util.Locale;

public class NumberFormatExample {

    private static final DecimalFormat numberFormatter;

    static {
        numberFormatter = (DecimalFormat) NumberFormat.getInstance(Locale.US);

        // Configure/override
        DecimalFormatSymbols symbols = numberFormatter.getDecimalFormatSymbols();
        symbols.setGroupingSeparator('\u00a0'); // non-breaking space
        symbols.setDecimalSeparator(',');
        numberFormatter.setDecimalFormatSymbols(symbols);
        numberFormatter.setMinimumFractionDigits(2);
    }

    public static String formatNumber(String rawNumber) {
        return numberFormatter.format(Long.parseLong(rawNumber) / 100d);
    }

    public static void main(String[] args) {
        String amount = "355128000";
        System.out.println(formatNumber(amount)); // 3 551 280,00
    }
}

Edit

It looks like you can use the French formatter, and specify just the min fraction digits.

import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.Locale;

public class NumberFormatExample {

    private static final DecimalFormat numberFormatter;

    static {
        numberFormatter = (DecimalFormat) NumberFormat.getInstance(Locale.FRENCH);

        // Configure
        numberFormatter.setMinimumFractionDigits(2);
    }

    public static String formatNumber(String rawNumber) {
        return numberFormatter.format(Long.parseLong(rawNumber) / 100d);
    }

    public static void main(String[] args) {
        String amount = "355128000";
        System.out.println(formatNumber(amount)); // 3 551 280,00
    }
}

I would forgo NumberFormat and just do it as follows using the France locale which matches your desired format.

String amount = "355128000";

UnaryOperator<String> format = str -> {
    long v = Long.parseLong(str);
    return String.format(Locale.FRANCE, "%,.2f", v / 100.);
};


System.out.println(format.apply(amount));

prints

3 551 280,00