DecimalFormat returns weird Character when formatting negative double

Question

i have a simple program that calculates a double value and prints it. whenever the value of that double is negative the first character of the outputted string is \u200e, ASCII value 8206. i cannot find anything about this online.

        System.out.println((int)DecimalFormat.getInstance().format(-1).charAt(0));
        System.out.println((int)DecimalFormat.getInstance().format(-1.0).charAt(0));
        System.out.println((int)NumberFormat.getInstance().format(1).charAt(0));
        System.out.println((int)NumberFormat.getInstance().format(0).charAt(0));

it prints as follows:

8206
8206
49
48

so i know that every negative value is given this weird prefix, but why? if i use String.format() it doesn't happen. no found documentation on this anywhere.

Anyone encountered this or knows how to explain?

Answer 1

You format a number into String, then take a first character charAt(0), cast it to int and actually print the ASCII code.

So it's no wonder that the code may produce a result like this:

45  // ASCII code of - in your default locale it's another character for negative values
45
49  // ASCII code of 1
48  // ASCII code of 0

8206 is a Unicode character for left-to-right mark.

It is very likely that this character is added to the NumberFormat / DecimalFormat to properly display values left-to-right when an RTL locale is applied as explained in this answer