Eight backslashes required to replace single backslash with double backslashes?

Question

This is a \"what the heck is going on here\" question. I don\'t actually need a solution.

I had to replace all single backslashes in a String with double backslashe

Answer 1

The second argument isn't a regex-string, but a regex-replacement-string, in which the backslash also has a special meaning (it is used to escape the special character $ used for variable interpolation and is also used to escape itself).

From The API:

Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string; see Matcher.replaceAll. Use Matcher.quoteReplacement(java.lang.String) to suppress the special meaning of these characters, if desired.

-- http://download.oracle.com/javase/6/docs/api/java/lang/String.html#replaceAll(...)