Java Regex - Capturing Groups - Tutorialspoint

Java Regex - Capturing Groups - Tutorialspoint

Capturing groups are a way to treat multiple characters as a single unit. They are created by placing the characters to be grouped inside a set of parentheses. For example, the regular expression (dog) creates a single group containing the letters "d", "o", and "g".

Capturing groups are numbered by counting their opening parentheses from the left to the right. In the expression ((A)(B(C))), for example, there are four such groups −

• ((A)(B(C)))
• (A)
• (B(C))
• (C)

To find out how many groups are present in the expression, call the groupCount method on a matcher object. The groupCount method returns an int showing the number of capturing groups present in the matcher's pattern.

There is also a special group, group 0, which always represents the entire expression. This group is not included in the total reported by groupCount.

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