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If you need to extract a part of string from the input string, we can use capture groups of regex. For this example, we'll start with a simple phone number regex: \d{3}-\d{3}-\d{4} If parentheses are added to the regex, each set of parentheses is considered a capturing group. In this case, we a...
A Pattern can be compiled with flags, if the regex is used as a literal String, use inline modifiers: Pattern pattern = Pattern.compile("foo.", Pattern.CASE_INSENSITIVE | Pattern.DOTALL); pattern.matcher("FOO\n").matches(); // Is true. /* Had the regex not been compiled case...
Generally To use regular expression specific characters (?+| etc.) in their literal meaning they need to be escaped. In common regular expression this is done by a backslash \. However, as it has a special meaning in Java Strings, you have to use a double backslash \\. These two examples will not ...
If you need to match characters that are a part of the regular expression syntax you can mark all or part of the pattern as a regex literal. \Q marks the beginning of the regex literal. \E marks the end of the regex literal. // the following throws a PatternSyntaxException because of the un-close...
To match something that does not contain a given string, one can use negative lookahead: Regex syntax: (?!string-to-not-match) Example: //not matching "popcorn" String regexString = "^(?!popcorn).*$"; System.out.println("[popcorn] " + ("popcorn".matches(r...
If you want to match a backslash in your regular expression, you'll have to escape it. Backslash is an escape character in regular expressions. You can use '\\' to refer to a single backslash in a regular expression. However, backslash is also an escape character in Java literal strings. To make a...

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