Regular Expression for a valid year in Java

Question

I have the following Regex:

^\d{4}$

I want to use it as a pattern in Java, for example:

"add year ^\d{4}$"

But I get an error because it contains a backslash. How can I ignore that?

So what is the error you're getting? The text of the error will generally suggest how to solve it. — daiscog, Feb 13 '17 at 12:10
See [What is the backslash character (\\\)?](http://stackoverflow.com/questions/12091506/what-is-the-backslash-character) — Wiktor Stribiżew, Feb 13 '17 at 12:11
i get an error that the year string does not match the pattern when i use ^\\d{4}$ — Rashad Ahmad, Feb 13 '17 at 12:18

score 1 · Answer 1 · answered Feb 13 '17 at 12:10

1

In Java strings, you have to escape the backslash:

"add year ^\\d{4}$"

answered Feb 13 '17 at 12:10

jqno

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when i do it this way the year string does not match it – Rashad Ahmad Feb 13 '17 at 12:18
The `^` matches the start of the input, so to have it in the middle of the string is probably what causes it not to match. You can try `"add year \\d{4}"`. – jqno Feb 13 '17 at 12:20

score 1 · Answer 2 · answered Feb 13 '17 at 12:20

As jqno stated, you need to escape the backslash. But there is another problem in your regex. ^ means beginning of the string. So, you are actually looking for add year [beginning of the string]\d{4}[end of the string].

Use this instead:

"add year \\d{4}$"

Regular Expression for a valid year in Java

2 Answers2