411 REFERENCE · Wikibooks
Java Programming/Regular Expressions
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Regular Expressions
__NOTOC__
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:
find(): find the next result.
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
*/
Replacements