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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

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Java Expert & Enterprise Software Architect

Mastering Regular Expressions in Java

## The `Matcher` class
The `Matcher` class also defines methods for replacing matched strings with a new replacement string. 
 
## Replacement methods
To replacing text in an input string, we use replacement methods.

`Matcher appendReplacement(StringBuffer sb, String replacement)` - Implements a non-terminal append-and-replace step.

Below is a code example demonstrating the use of the `appendReplacement()` method:


# The `Matcher` class
The `Matcher` class also defines methods for replacing matched strings with a new replacement string. 
 
# Replacement methods
To replacing text in an input string, we use replacement methods.

`Matcher appendReplacement(StringBuffer sb, String replacement)` - Implements a non-terminal append-and-replace step.

Below is a code example demonstrating the use of the `appendReplacement()` method:


In this lesson, you will learn how to perform the String replacement methods of the Matcher class and capture groups in the regular expressions.

Introduction

Java Regex APIs

Building Blocks of Regular Expressions

Course Wrap Up

Replacement Methods of Matcher Class

The `Matcher` class