Josh Juneau - Java 17 Recipes: A Problem-Solution Approach

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This book teaches you many features of the Java programming language, from those introduced in Java 1.0 to those that made their way to Java 17. Released in September 2021, the Java Development Kit (JDK) 17 is a long-term support (LTS) release (i.e., a stable release supported for several years). Java is backward compatible. Even if a new Java version is released every six months, you do not need to learn a specific version. Rather, you need to get a good foundation in all language features to use them in your applications. Since the last edition of this book, many enhancements have occurred. This book includes new recipes covering features from Java 9 to Java 17. The recipes you implement always use open source tools, such as OpenJDK and Eclipse.

This book covers the fundamentals of Java development, such as installing the JDK, writing classes, and running applications. It delves into essential topics such as the development of object-oriented constructs, exception handling, unit testing, and localization. This book can be used as a guide for solving problems that ordinary Java developers may encounter at some point, as a starting point for anyone beginning the study of Java for the first time, or for developers who have used the Java language for some time to refine Java development skills. It will also be useful to help advanced Java application developers to learn a thing or two regarding the language's new features and perhaps even stumble upon some techniques that were not used in the past. This book discusses a broad range of topics, and the solutions to the problems covered are concise. Whatever your skill level, this book is good to have close at hand as a reference for solutions to those problems that you encounter in your daily programming.

The Java programming language was introduced in 1995 by Sun Microsystems. Derived from languages such as C and C++, Java was designed to be more intuitive and easier to use than older languages, specifically due to its simplistic object model and automated facilities such as memory management. At the time, Java drew the interest of developers because of its object-oriented, concurrent architecture, excellent security and scalability, and applications developed in the Java language could run on any operating system that contained a JVM. Since its inception, Java has been described as a language that allows developers to write once, run everywhere as code is compiled into class files that contain bytecode. The resulting class files can run on any compliant JVM. This concept made Java an immediate success for desktop development, which later branched off into different technological solutions over the years, such as web-based applications. Today, Java is deployed on a broad range of devices, including mobile phones, printers, medical devices, and so on.

The Java platform consists of a hierarchy of components, starting with the JDK, which is composed of the Java Runtime Environment (JRE), the Java programming language, and platform tools that are necessary to develop and run Java applications. The JRE contains the JVM, plus the Java application programming interfaces (APIs) and libraries that assist in developing Java applications. The JVM is the base upon which compiled Java class files run and is responsible for interpreting compiled Java classes and executing the code. Every operating system capable of running Java code has its own version of the JVM. To that end, the JRE must be installed on any system running local Java desktop or stand-alone Java applications. But there is no problem because JRE implementations are provided for most major operating systems. Each operating system can have its own flavor of the JRE. For instance, mobile devices can run a scaled-down version of the full JRE optimized to run Java Mobile Edition (ME) and Java SE embedded applications. The Java platform APIs and libraries are a collection of predefined classes used by all Java applications. Any application that runs on the JVM makes uses the Java platform APIs and libraries. This allows applications to use the predefined and loaded functionality into the JVM and leaves developers with more time to worry about the details of their specific application. The classes that comprise the Java platform APIs and libraries allow Java applications to use one set of classes to communicate with the underlying operating system. As such, the Java platform takes care of interpreting the set of instructions provided by a Java application into operating system commands that are required for the machine on which the application is being executed. This creates a facade for Java developers to write code against to develop applications that can be written once and run on every machine that contains a relevant JVM.

The JVM and the Java platform APIs and libraries play key roles in the life cycle of every Java application. Entire books have been written to explore the platform and JVM. This book focuses on the Java language, which is used to develop Java applications, although the JVM and Java platform APIs and libraries are referenced as needed. The Java language is a robust, secure, and modern object-oriented language that can develop applications to run on the JVM. The Java programming language has been refined over several iterations, and it becomes more powerful, secure, and modern with each new release.