Book Image

Learning Java Lambdas

By : Toby Weston
Book Image

Learning Java Lambdas

By: Toby Weston

Overview of this book

In this short book, we take an in-depth look at lambdas in Java, and their supporting features. The book covers essential topics, such as functional interfaces and type inference, and the key differences between lambdas and closures. You will learn about the background to functional programming and lambdas, before moving on to understanding the basic syntax of lambdas and what differentiates these anonymous functions from standard anonymous classes. Lastly, you'll learn how to invoke lambdas and look at the bytecode generated. After reading this book, you'll understand lambdas in depth, their background, syntax, implementation details, and how and when to use them. You'll also have a clear knowledge of the difference between functions and classes, and why that's relevant to lambdas. This knowledge will enable you to appreciate the improvements to type inference that drive a lot of the new features in modern Java, and will increase your understanding of method references and scoping.
Table of Contents (10 chapters)

Code examples


Lets have a look at the bytecode produced for some examples.

We're going to look at the bytecode for four distinct blocks of functionality based on the example we looked at in lambdas vs closures section.

We'll explore:

  1. A simple anonymous class.

  2. An anonymous class closing over some variable (an old style closure).

  3. A lambda with no arguments.

  4. A lambda with arguments.

  5. A lambda closing over some variable (a new style closure).

The example bytecode was generated using the javap command line tool. Only partial bytecode listings are shown in this section, for full source and bytecode listings, see Appendix A. Also, fully qualified class names have been shortened to better fit on the page.