How to add spaces to a string and reduce numbers after a comma?

Question

Java

At the input to the method, a string like 3125126.356356356 is supplied

public static String mySplit(String string) {
        String str = null;
        str = String.format("%.3f", Double.parseDouble(string));
        return str;
   }

at the output we get 3125126.356 It is
necessary to get 3 125 126.356
That is, add spaces to the left side before the decimal point so that thousandths can be visually determined in the program

Answer 1

I think one can use DecimalFormat + DecimalFormatSymbols::setDecimalSeparator