Book Image

Java 9 Regular Expressions

By : Anubhava Srivastava
Book Image

Java 9 Regular Expressions

By: Anubhava Srivastava

Overview of this book

Regular expressions are a powerful tool in the programmer's toolbox and allow pattern matching. They are also used for manipulating text and data. This book will provide you with the know-how (and practical examples) to solve real-world problems using regex in Java. You will begin by discovering what regular expressions are and how they work with Java. This easy-to-follow guide is a great place from which to familiarize yourself with the core concepts of regular expressions and to master its implementation with the features of Java 9. You will learn how to match, extract, and transform text by matching specific words, characters, and patterns. You will learn when and where to apply the methods for finding patterns in digits, letters, Unicode characters, and string literals. Going forward, you will learn to use zero-length assertions and lookarounds, parsing the source code, and processing the log files. Finally, you will master tips, tricks, and best practices in regex with Java.
Table of Contents (15 chapters)
Title page
About the Author
About the Reviewer
Customer Feedback
Free Chapter
Getting Started with Regular Expressions

The intersection of character classes

The intersection operation on character classes results in a composite class that contains every character allowed by all of its operand (inner) classes or, in other words, matches characters that belong to all the character classes in the composite character class pattern. The intersection operator is as follows:


For example, consider the following composite character class using the && operator:


This matches any character that is in the range of A to Z and is one of the single P, Q, or R characters. However, the preceding regular expression can also be simply written as follows:


The following composite character class using intersection matches the digits, 5 and 6, since only these two digits belong to all the three character classes:


To see this regex in action, let's use this complete code:

package example.regex; 
import java.util.regex.*; 
public class IntersectionExample...