How to use Regular Expressions in Java – String Class Tutorial

We can use Regular Expressions on String class in Java. It can be applied on the following Methods.

1. public boolean matches(String regex) – Tells whether or not this string matches the given regular expression.
2. public String[] split(String regex,int limit) – Splits this string around matches of the given regular expression.
3. public String[] split(String regex) – Splits this string around matches of the given regular expression.
4. replaceAll(String regex, String replacement) – Replaces each substring of this string that matches the given regular expression with the given replacement.
5. replaceFirst(String regex, String replacement) – Replaces the first substring of this string that matches the given regular expression with the given replacement.

Regex in String Class – Tutorial

package com.javaindetail.PatternTutorial;

public class StringRegexTutorial {

  public static final String TEXT_FOR_REGEX = "This is a technical blog about java. javaindetail.com is a technical blog. Explore everything in detail";

  public static void main(String[] args) {
    
    System.out.println(TEXT_FOR_REGEX.matches("\w.*"));
    
    // splitting the string with spaces
    String[] splitString = (TEXT_FOR_REGEX.split("\s+"));
    
    System.out.println(splitString.length);
    
    for (String string : splitString) {
      System.out.println(string);
    }
    
    // replace all whitespace with tabs
    System.out.println(TEXT_FOR_REGEX.replaceAll("\s+", "t"));
  }
}

Output

true
16
This
is
a
technical
blog
about
java.
javaindetail.com
is
a
technical
blog.
Explore
everything
in
detail
This	is	a	technical	blog	about	java.	javaindetail.com	is	a	technical	blog.	Explore	everything	in	detail