Java regex validate a string consisting of repeated sequences of comma separated digits enclosed in parentheses

Question

I have an input containing repeated pattern like this:

 (3,5)(6,7)(8,9).....

I am working on a regex to validate the above string pattern.

I tried:

Pattern.compile("\\((\\d+),(\\d+)\\)")

And? The regex seems to be ok more or less. What is the problem? — Amongalen, Apr 24 '20 at 07:13
@WiktorStribiżew You either need to add `^` and `$`, or you need to clarify that it must be used with `matches()`, not `find()`. — Andreas, Apr 24 '20 at 07:18

score 1 · Answer 1 · answered Apr 24 '20 at 07:34

If you have a specific pattern that may repeat one or more times in a string, and you want to make sure your string only consists of the repeated occurrences of the same pattern, you may use

^(?:YOUR_PATTERN)+$
\A(?:YOUR_PATTERN)+\z

Note that $ also matches before a final newline char, that is why \z anchor is preferred when you need to match the very end of the string.

If you allow an empty string use the * quantifier instead of +:

^(?:YOUR_PATTERN)*$
\A(?:YOUR_PATTERN)*\z

In this case, the YOUR_PATTERN is $\d+,\d+$, thus, the repeated sequence validating pattern will be \A(?:$\d+,\d+$)+\z.

In Java, you may omit the ^/$ and \A/\z anchors when validating a string with .matches() method since it requires a full string match:

boolean isValid = text.matches("(?:\\(\\d+,\\d+\\))+");

Or, decalre the Pattern class instance first and then create a matcher with the string as input and run Matcher#matches()

Pattern p = Pattern.compile("(?:\\(\\d+,\\d+\\))+");
Matcher m = p.matcher(text);
if (m.matches()) {
    // The text is valid!
}

Java regex validate a string consisting of repeated sequences of comma separated digits enclosed in parentheses

1 Answers1