Java examples on Java Regex

• How do I split-up string using regular expression?
• How do I create a string search and replace using regex?
• How do I do regular expression in Java?
• How do I check if a string starts with a pattern?
• How do I determine if a string match a pattern exactly?
• How do I use logical OR operator in regex?
• How do I find and replace string?
• How do I write embedded flag expression?
• How do I do boundary matching in regex?
• How do I use capturing groups in regex?
• How do I match a regex pattern in case insensitive?
• How do I count the number of capturing groups?
• How do I use quantifier in regex?
• How do I write simple character class regex?
• How do I write character class subtraction regex?
• How do I write negated character class regex?
• How do I use possessive quantifier regex?
• How do I write union character class regex?
• How do I write range character class regex?
• How do I use predefined character classes regex?
• How do I use reluctant quantifier regex?
• How do I write character class intersection regex?
• How do I combile character classes with quantifier?
• How to remove non ASCII characters from a string?
• How to truncate a string after n number of words?

How do I use predefined character classes regex?

In regex, you also have a number of predefined character classes that provide you with a shorthand notation for commonly used sets of characters.

Here are the list:

• .  : represent any character.
• \d : represent any digit, shorthand for [0-9]
• \D : represent a non digit, [^0-9]
• \s : represent a whitespace character [^\s]
• \S : represent any non whitespace character
• \w : represent word character [a-zA-Z_0-9]
• \W : represent a non word character

package org.kodejava.example.util.regex;

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

public class PredefinedCharacterClassDemo {
    public static void main(String[] args) {
        //
        // Define regex that will search a whitespace followed by f 
        // and two any characters.
        //
        String regex = "\\sf..";

        //
        // Compiles the pattern and obtains the matcher object.
        //
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(
                "The quick brown fox jumps over the lazy dog");

        //
        // 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());
        }
    }
}

This program output the following result:

Text " fox" found at 15 to 19.