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Regular expressions describe a pattern of characters used for searching a string. They are very useful for parsing information like dates, phone numbers, or zip codes from important text files such as code files, log files, spreadsheets, or documents. 

Below are the most common use cases of regular expressions: 
- Data validation of data fields or values like phone numbers, zip codes, email addresses, etc.
- Information extraction from text files for further processing
- Pattern matching of strings or textual information
- Search and replace operation on texts

This course will teach you how to perform pattern matching with a regular expression using a Java API for these practical use cases.

Tarun Telang

Tarun Telang is a passionate software engineer, leader, architect, author, and active contributor in various online technical forums.

Java Expert & Enterprise Software Architect

Mastering Regular Expressions in Java

## Character classes

A character class is a group of characters that represent patterns. It is made up of brackets followed by a series of characters, e.g. `[aeiou]`, This would match any vowel within your string. 

You can specify multiple options in one character class, e.g. `[a-zA-Z0-9]` will match upper and lower case letters and numbers within your string. 

Below are few examples of simple character classes: 

### The character class `[abc]`

The character class `[abc]` will match any one character from the set {`a`, `b`, `c`}.
Execute the code below to see this in action. 

# Character classes

A character class is a group of characters that represent patterns. It is made up of brackets followed by a series of characters, e.g. `[aeiou]`, This would match any vowel within your string. 

You can specify multiple options in one character class, e.g. `[a-zA-Z0-9]` will match upper and lower case letters and numbers within your string. 

Below are few examples of simple character classes: 

## The character class `[abc]`

The character class `[abc]` will match any one character from the set {`a`, `b`, `c`}.
Execute the code below to see this in action. 

Learn how to create pattern objects using character classes and search for the given pattern within any text.

Introduction

Java Regex APIs

Building Blocks of Regular Expressions

Course Wrap Up

Pattern Matching Using Character Classes

Character classes

The character class `[abc]`