Part I describes how Java as a language compares to mainframe languages. Object -oriented concepts are explained in contrast to structured programming and third generation procedural languages, such as COBOL or PL/I. It teaches mainframe programming using Java code snippets side by side with COBOL and PL/I snippets that perform the same functions. Through this stepped approach, the reader will learn to build a complete Java application using the Sun Java Development Kit (JDK).

Part II covers IBM's OS/390 Java implementation and the specific packages for IBM like CICS (used for transaction processing), IMS (for transaction processing and hierarchical databases), DB2 (for relational databases) and VSAM (for sequential and indexed direct access).

Part III focuses on advanced Java programming to create the middleware that allows access to the mainframe date. The reader will also become familiar with Java classes and Enterprise Java Beans.