convert newlines to windows newlines [duplicate]

Question

I want to convert all newlines in my input string to windows newlines (\r\n). So I want to apply the following mapping:

\r\n  -> \r\n
\r    -> \r\n
\n    -> \r\n

How should this be done?

Answer 1

You could try replacing on the following pattern:

\r(?!\n)|(?<!\r)\n

This would match carriage return which is not followed by newline (i.e. \r but not \r\n CRLF). That failing, it would match just a single newline character, not preceded by carriage return (again, not CRLF).

Usage:

input.replaceAll("\r(?!\n)|(?<!\r)\n", "\r\n");

Answer 2

I would put \r\n, \r, and \n as 3 alternatives separated by |. By putting \r\n first, the other alternatives will not match when there is a \r\n sequence.

input.replaceAll("\r\n|\r|\n", "\r\n")