Regular Expression: Zip Code only 9 or 10 Digits with Dash

Question

We are allowing US Zip Codes as only (1) 9 digits, or (2) 10 digits with a dash before the last 4 digits.

The following regexp gives a compilation error:

private static final String USZIPCODE_MATCH_FORMAT_REGEXP = "^\d{5}[\\-]?\d{4}$";

Invalid escape sequence

Answer 1

In Java you need to escape the \ as well. So, you need

"^\\d{5}[\\-]?\\d{4}$"

Also, you can specify the hyphen simply as

"^\\d{5}-?\\d{4}$"

The - is not special when used outside [].