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Explore Clojure programming language and its multithread style

Discover the fundamentals of the Clojure programming language and its Java-specific uses and tool pairings to see if this multithread programming approach is a fit for your team.

The Clojure programming language, a dialect of Lisp, combines accessibility and simplicity with an infrastructure designed for multithread programming.

In contrast to object-oriented languages that encapsulate data as custom objects, Clojure doesn't package data in layers of class definitions, inheritance and type declarations. Instead, it ensures developers can create entire information models using built-in immutable data structures. Developers can use Clojure to grow their programs with data loaded, while the team tests the software and fixes bugs. It can all occur while they create features and add functions.

Clojure is designed for Java virtual machines (JVM), Common Language Runtime and JavaScript engines. It's compiled and dynamic. Clojure is available as installers and convenience scripts for use on Linux and macOS and as a cursive IntelliJ IDEA plugin for Windows programmers.

To get started with the Clojure programming language, you should first get familiar with Lisp-based concepts at play, such as "code as data," concurrency and immutability. Then, get familiar with the main Clojure resources and tools for programmers.

Code as data, concurrency and immutability

Clojure's uniform syntax, macro capabilities and overall structure as a dialect of Lisp provide programming speed and concision. Meta programming is facilitated by the code-as-data concept, which centers on the notion that the programming structure of the language mimics the syntax.

Developers working with a code-as-data language apply the same operations and transformations to a block of code as though it was a native data structure. They manipulate content programmatically, so the code works like any other data structure within an environment.

Clojure's concurrency programming takes advantage of multicore processing power common in servers. With concurrency, multiple operations run sequentially on multiple cores, overlapping as needed, so that a process is executed correctly. By consecutively calling methods rather than running operations one at a time, developers can ensure the program has higher throughput and performance, with less overhead and latency.

More cost-effective than parallel programming -- a subset of concurrency wherein a single process is handled by multiple cores simultaneously -- Clojure's concurrent programming design enacts multiple threads of control independently. Using powerful concurrency primitives, Clojure developers can easily take advantage of multiple cores.

Clojure's effectiveness can also be attributed to a reliance on immutable data structures and collections. As developers add, update and remove elements, Clojure retains the same value for those collections.

Immutability guarantees that all of the possible properties of objects are defined at the time of their construction and can't be changed subsequently. Immutability enables threads to share data, and this makes it well-suited to developing multithreaded programs. And there's no risk of multiple threads writing to the data structure at the same time.

Through multithreading, programmers can ensure cost-effective execution and easy communication within each set of instructions that are given to the machine.

Development environments, editors and other tools

Clojure offers a range of tools to mold the expressive programming language so that the vocabulary and grammar align effectively with a problem domain. For example, Clojure's dynamic system provides the ability to constantly redefine functions, multi-methods, type hierarchies and even method implementations while a program is running.

Clojure's approach to language enables a high degree of experimentation and exploration that's often limited in more static languages and long compilation times.

Whether programmers face single or multithreaded issues, Clojure provides a set of tools for code clarity. For example, Leiningen manages dependencies, deployments and versioned releases for projects exclusively in Clojure. As a build automation tool, Leiningen enables programmers to maintain conventions, clearly depicting a project to other developers who can then ramp up quickly.

Highly aligned with Maven, Leiningen is the tool of choice for automatically managing dependencies on all Java libraries. Developers can be more productive if they use Maven to execute relatively complex builds, tests and deployments in a single command.

The Clojure Emacs text editor connects programmers' code with a language shell -- also known as a read/evaluate/print loop -- so they can try out the code immediately as it's written. Use the Emacs with CIDER, or the Clojure Interactive Development Environment that Rocks, to stand up a dynamic workflow environment where programmers can continually add to and redefine applications. CIDER includes an IntelliJ IDEA extension that provides a more traditional Java integrated development environment experience.

Work with ClojureScript

ClojureScript, a JavaScript compiler for Clojure, suits single-page applications that target a fluent web-based user experience similar to a desktop application. ClojureScript compiles to JavaScript for use in a browser and other environments where JavaScript runs, including the Node.js JavaScript runtime on the server.

ClojureScript handles data cleanly, offers flexible functions and can customize functions as needed. It follows the same uniform syntax design as Clojure and offers large libraries of functions on primitive data types.

As an invention of the Clojure language for the JavaScript platform, ClojureScript compiles to JavaScript and runs in the browser or Node.js environments. ClojureScript is most known for creating highly interactive and dynamic user interfaces for web and mobile platforms. And while Clojure and ClojureScript are hosted in different environments, they share similarities by emphasizing simple syntax, immutable data structures, functional paradigms and a powerful standard library.

Several libraries in ClojureScript are widely popular, and developers adopting Clojure should research them. For example, Reagent offers a minimalistic React library to build UIs. In addition, Rum provides a simple HTML UI library, and Om makes use of object-oriented structures to enhance React through immutability.

Designed to be practical with a tight relationship to Java, Clojure developers can benefit immediately from exciting developments in Java, and they can have access to the same standard types used in any Java application.

This was last published in June 2019

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