Java Regular Expressions

Regular expressions (regex) in Java are a powerful and essential tool for pattern matching and text manipulation. Whether you’re validating inputs, parsing logs, or processing large datasets, Java’s java.util.regex package offers a concise way to handle complex string operations.

In this article, will cover the basics of regex, explore core components like Pattern and Matcher, and dive into real-world use cases and advanced concepts such as quantifiers, boundary matchers, and more.

Java Regex Basics

Java regular expressions are part of the java.util.regex package. A regular expression is a sequence of characters that forms a search pattern. You can use it to check if a string contains a pattern, extract parts of strings, or replace content.

Key Classes:

• Pattern: Represents the compiled regex pattern.
• Matcher: Performs matching operations on a string using a Pattern.

import java.util.regex.*;

public class Main {
    public static void main(String[] args) {
        Pattern pattern = Pattern.compile("fo+");
        Matcher matcher = pattern.matcher("foo bar foobar fobar");
        while (matcher.find()) {
            System.out.println("Match found: " + matcher.group());
        }
    }
}

Output:

Match found: foo
Match found: foo

Pattern Syntax and Symbols