Regex In Java

You can use regular expressions (regex) to perform pattern matching and manipulate strings. Regular expressions are powerful tools for tasks like string validation, searching, and extraction based on patterns.

To work with regular expressions in Java, you’ll typically use the java.util.regex package, which provides classes like Pattern and Matcher. A regular expression can be a single character, or a more complicated pattern.

1. Creating a Regular Expression Pattern:

To use regex in Java, you first need to create a Pattern object, which represents the regex pattern. You can do this using the Pattern.compile() method.

Example :-

import java.util.regex.Pattern;

Pattern pattern = Pattern.compile(“abc”); // Example pattern: matches “abc” in a string

2. Matching Strings :-

You can use the Matcher class to match a regex pattern against a string.

Example :-

import java.util.regex.Matcher;

String text = “The abc is here.”;

Matcher matcher = pattern.matcher(text);

while (matcher.find())

{

    System.out.println(“Found: ” + matcher.group());

}

In this example, the find() method is used to find the next occurrence of the pattern in the input string.

3. Common Regex Patterns :-

Here are some common regex patterns and their meanings:

• • . :- Matches any character.
  • : :- Matches zero or more occurrences of the preceding character or group.
  • + :- Matches one or more occurrences of the preceding character or group.
  • ? : – Matches zero or one occurrence of the preceding character or group.
  • [] :- Matches any character inside the brackets.
  • [^] :- Matches any character NOT inside the brackets.
  • \\d :- Matches a digit (0-9).
  • \\w :- Matches a word character (a-z, A-Z, 0-9).
  • \\s :- Matches a whitespace character (space, tab, newline, etc.).
  • It implements the MatchResult It is a regex enginewhich is used to perform match operations on a character sequence.

Matcher class:-

The Matcher class is typically associated with programming languages and libraries that provide support for regex pattern matching. It’s not a universal class found in all programming languages, but it’s commonly used in languages like Java.

The Matcher class is part of the Java regular expressions package (java.util.regex) and is used to perform pattern matching operations with regular expressions.