Java 8 in Action

This book is the Chinese translation of Java 8 in Action, built around the landmark new features introduced when Java 8 was released in March 2014, with the goal of helping developers already familiar with Java actually use the new syntax in everyday projects. The book has four parts. Part 1, Fundamentals, begins with why you should care about Java 8, explaining the motivations for Java's evolution against the backdrop of multicore processors and big data applications, then uses the running example of filtering apples to explain behavior parameterization, and systematically introduces lambda expressions, method references, functional interfaces and type inference, and explains why default methods are the key that allowed the collections libraries to evolve. Part 2, Functional-style Data Processing, focuses on the Stream API, including filtering, slicing, mapping, finding and matching, reducing, numeric streams and building streams, as well as using collectors to aggregate stream results into collections, groups and partitions; it also explains how parallel streams work and where they apply. Part 3, Effective Java 8 Programming, discusses refactoring existing code with lambdas and streams, making code more readable, testable and debuggable, and introduces Optional, CompletableFuture and the new date and time API. Part 4, Beyond Java 8, moves past specific APIs to the mindset and techniques of functional programming, persistent data structures and lazy evaluation, and uses a comparison with Scala to show hybrid object-oriented and functional styles, ending with a review of Java 8 language features and a look at Java's future; appendices cover library updates, annotations, performing multiple stream operations concurrently, and how lambdas are implemented in JVM bytecode. The book includes many runnable code examples, end-of-chapter summaries, and interactive sections such as quizzes and quick checks so readers can test their understanding as they read.