Java Regular Expression Tutorial - Java Regex Quantifiers

We can specify the number of times a character in a regular expression may match the sequence of characters.

To express a pattern "one digit or more" using a regular expression, we can use the quantifiers.

Quantifiers and their meanings are listed in the following Table.

*Zero or more times
+One or more times
?Once or not at all
{m}Exactly m times
{m,}At least m times
{m, n}At least m, but not more than n times

The quantifiers must follow a character or character class.


import java.util.regex.Matcher;
import java.util.regex.Pattern;
//from w  ww  . java 2s  .co m
public class Main {
  public static void main(String[] args) {
    // A group of 3 digits followed by 7 digits.
    String regex = "\\b(\\d{3})\\d{7}\\b";

    // Compile the regular expression
    Pattern p = Pattern.compile(regex);

    String source = "12345678, 12345, and 9876543210";

    // Get the Matcher object
    Matcher m = p.matcher(source);

    // Start matching and display the found area codes
    while (m.find()) {
      String phone =;
      String areaCode =;
      System.out.println("Phone: " + phone + ", Area  Code:  " + areaCode);

The code above generates the following result.

Example 2

* matches zero or more d.

import java.util.regex.Pattern;
//  w  ww .  j  a v a  2 s . c  om
public class Main {
  public static void main(String args[]) {

    String regex = "ad*";
    String input = "add";

    boolean isMatch = Pattern.matches(regex, input);

The code above generates the following result.