Escaping null byte next to two zeroes

Question

I need to escape the following sequence defined as a static final

final String POSIX_SIGNATURE = "ustar".concat("\0").concat("00");

How would I escape this without using the .concat() method nor the + string operator?

final String POSIX_SIGNATURE = "ustar\000"; 

This is not valid, not the same as the first one.

final String POSIX_SIGNATURE = "ustar\0\00"; 

Nor is this one either.

Answer 1

Use a unicode escape sequence:

"\u000000"

This is the NUL character (\u0000), followed by two 0's.

Answer 2

Darth Android has the solution, but here is the reason your attempts didn't work the way you expected.

The reason the null character is represented by \0 isn't because it's a special escape sequence just for the null character; it's because it's an octal escape sequence of up to 3 octal digits.

Your string "ustar\000" has 1 null character on the end, \000, and your string "ustar\0\00" has 2 null characters on the end, \0 and \00.

The solution is as previously mentioned by Darth Android -- use a Unicode escape, which has exactly 4 hex digits, so that extra 0 characters are just that -- 0 characters. The \u0000 is the null character, and the 5th and 6th 0s are literal 0 characters.

Answer 3

You can also use

"ustar\00000"

\ can be followed by up to 3 octal digits (between 000 and 377), so this is \000 followed by "00".

Alternatively, you could do

"ustar\0\600"

This is \0 followed by \60 (octal for '0') followed by '0'.