How do I use capturing groups in regex?
Date: 2010-11-04. Category: Java Regex examples. Hits: 4K time(s).
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".
Regular expressions can also define other capturing groups that correspond to parts of the pattern. Each pair of parentheses in a regular expression defines a separate capturing group in addition to the group that the whole expression defines.
package org.kodejava.example.util.regex;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class CapturingGroupDemo {
public static void main(String[] args) {
//
// Define regex to find the word 'the' or 'quick'
//
String regex = "(the)|(quick)";
String text = "the quick brown fox jumps over the lazy dog";
//
// Compiles the given regular expression into a pattern and
// Creates a matcher that will match the given input against
// this pattern.
//
Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(text);
//
// Find every match and print it
//
while (matcher.find()) {
System.out.format("Text \"%s\" found at %d to %d.%n",
matcher.group(), matcher.start(), matcher.end());
}
}
}
The result of the program are:
Text "the" found at 0 to 3. Text "quick" found at 4 to 9. Text "the" found at 31 to 34.