Why does this Java regex cause "illegal escape character" errors?

Question

I'm working on a solution to a previous question, as best as I can, using regular expressions. My pattern is

"\d{4}\w{3}(0[1-9]|[12][0-9]|3[01])([01][0-9]|2[0-3])([0-5][0-9]){2}" 

According to NetBeans, I have two illegal escape characters. I'm guessing it has to do with the \d and \w, but those are both valid in Java. Perhaps my syntax for a Java regular expression is off...

The entire line of code that is involved is:

userTimestampField = new FormattedTextField(   new RegexFormatter(     "\d{4}\w{3}(0[1-9]|[12][0-9]|3[01])([01][0-9]|2[0-3])([0-5][0-9]){2}" )); 

Answer 1

Assuming this regex is inside a Java String literal, you need to escape the backslashes for your \d and \w tags:

"\\d{4}\\w{3}(0[1-9]|[12][0-9]|3[01])([01][0-9]|2[0-3])([0-5][0-9]){2}" 

This gets more, well, bonkers frankly, when you want to match backslashes:

public static void main(String[] args) {             Pattern p = Pattern.compile("\\\\\\\\"); //ERM, YEP: 8 OF THEM     String s = "\\\\";     Matcher m = p.matcher(s);     System.out.println(s);     System.out.println(m.matches()); }  \\ //JUST TO MATCH TWO SLASHES :( true