This concise book is for library programmers who want to learn to use MARC4J to process bibliographic data. MARC4J is an open source software library for working with MARC, MARCXML and related bibliographic standards in Java. The library is designed to bridge the gap between MARC and XML. Crosswalking provides useful information for both developers learning about MARC4J for the first time and developers returning for reference and more advanced material. The chapters provide many reusable examples, while appendixes provide a reference to the API and the command-line utilities.