Generics are a powerful, and sometimes controversial, new feature of the Java programming language. This part of the book describes generics, using the Collections Framework as a source of examples. A comprehensive introduction to the Collections Framework appears in the second part of the book.
The first five chapters focus on the fundamentals of generics. Chapter 1 gives an overview of generics and other new features in Java 5, including boxing, foreach loops, and functions with a variable number of arguments. Chapter 2 reviews how subtyping works and explains how wildcards let you use subtyping in connection with generics. Chapter 3 describes how generics work with the Comparable interface, which requires a notion of bounds on type variables. Chapter 4 looks at how generics work with various declarations, including constructors, static members, and nested classes. Chapter 5 explains how to evolve legacy code to exploit generics, and how ease of evolution is a key advantage of the design of generics in Java. Once you have these five chapters under your belt, you will be able to use generics effectively in most basic situations.
The next four chapters treat advanced topics. Chapter 6 explains how the same design that leads to ease of evolution also necessarily leads to a few rough edges in the treatment of casts, exceptions, and arrays. The fit between generics and arrays is the worst rough corner of the language, and we formulate two principles to help you work around the problems. Chapter 7 explains new features that relate generics and reflection, including the newly generified type Class<T> and additions to the Java library that support reflection of generic types. Chapter 8 contains advice on how to use generics effectively in practical coding.We consider checked collections, security issues, specialized classes, and binary compatibility. Chapter 9 presents five extended examples, looking at how generics affect five well-known design patterns: Visitor, Interpreter, Function, Strategy, and Subject-Observer.
Chapter 1, Introduction
Chapter 2, Subtyping and Wildcards
Chapter 3, Comparison and Bounds
Chapter 4, Declarations
Chapter 5, Evolution, Not Revolution
Chapter 6, Reification
Chapter 7, Reflection
Chapter 8, Effective Generics
Chapter 9, Design Patterns
