This book is for Java developers who would like to understand and use regular expressions. If you are dealing with text processing problems, such as text validation, searching, and text manipulation, then learning regex is very important for you to make your job easier. This book does not expect readers to have any prior regex knowledge, since the book will cover every aspect of regex, starting from the absolute basics of regex. However, a basic knowledge of Java is assumed in order to be able to write and execute the example programs provided in the book.