Regular Expressions

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The regular expressions (regex) are provided by the package java.util.regex.

Researches

The Pattern class offers the function matches which returns true if an expression is found into a string.

For example, this script returns the unknown word preceding a known word:

import java.util.regex.Pattern;
public class Regex {
	public static void main(String[] args) {
		String s = "Test Java regex for Wikibooks.";
		System.out.println(Pattern.matches("[a-z]* Wikibooks",s));
    }
}
// Displays: "for Wikibooks"

The Matcher class allows to get all matches for a given expression, with different methods:

1. find(): find the next result.
2. group(): displays the result.

For example, this script displays the HTML b tags contents:

import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class Regex {
	public static void main(String[] args) {
		String s = "Test <i>Java</i> <b>regex</b> for <b>Wikibooks</b>.";
		Pattern p = Pattern.compile("<b>([^<]+)</b>");
		Matcher m = p.matcher(s);
		while(m.find()) {
			System.out.println(m.group());
			System.out.println(m.group(1));
		}
	}
}
/* Displays:
 <b>regex</b>
 regex
 <b>Wikibooks</b>
 Wikibooks
*/