OpenJDK (the Open Java Development Kit) is an open-source implementation of the Java Platform in the Standard Edition, which acts as the foundation for building and deploying Java applications. It gives you access to comprehensive language libraries, a Java Virtual Machine (JVM), and different tools and utilities that help you create applications for desktop, web, or even enterprise environments.
As an open-source initiative, OpenJDK is completely free, but it has an engaged community and partners (like Oracle, Amazon, Azul, etc.) that contribute innovative solutions, performance improvements, and detailed documentation of this vibrant ecosystem. Thanks to that, this utility is an essential tool for programmers of any experience level.
You can download OpenJDK on Windows, macOS, and Linux, and the tool is available for free under the GPL license so that you can review the source, submit fixes and patches, and even modify it if you have a specialized use case. OpenJDK complies with Java standards and specifications to work smoothly with other Java runtimes.
Why should I download OpenJDK?
OpenJDK allows you to write your applications once and run them anywhere, as it’s a mature and industrial-grade Java platform. With it, you can create portable, scalable, and secure applications for various platforms and operating systems. The foundation of this tool is the Java Virtual Machine (JVM), which essentially takes your Java bytecode and interprets it into native machine instructions. OpenJDK also uses JIT (Just-In-Time) compilation, adaptive optimization, and various garbage collection strategies so that you can get a smooth runtime and performance even under a heavy load.
With OpenJDK, you get a full implementation of Java SE standard with all the core libraries (java.lang, java.util, java.io, etc.), networking, threading, date/time handling, and other essential APIs. It’s a great and consistent Java solution if you need to develop software that runs on different systems and configurations without significant changes.
As a developer, you’ll also appreciate that OpenJDK fully supports Java Platform Module System (JPMS), allowing you to include only necessary modules in runtime environments. As a result, you’ll get a reduced app size and better startup time, which would be crucial if you’re working on microservices or IoT deployments. OpenJDK includes a Java compiler (javac), an API documentation generator (javadoc), an interactive REPL for testing code snippets (jshell), jlink to build custom runtime images as well as jmod for packaging different Java modules. The platform is also compatible with various development tools so that you can use it with Eclipse, IntelliJ IDEA, NetBeans, and Visual Studio Code.
If you need to work with cloud environments, OpenJDK can be used in services like AWS Lambda, Google Cloud Functions, and Azure App Services, and you can deploy it through Docker containers and Kubernetes clusters. For those looking for LTS, you can get different distributions based on OpenJDK, like Adoptium Temurin, Amazon Corretto, and Red Hat OpenJDK, which include testing, updates, and security fixes.
OpenJDK is also compatible with a lot of different languages, even the ones based on JVM. Kotlin, Scala, Groovy, JRuby, and Clojure can be compiled into Java bytecode and then run smoothly with OpenJDK. It’s a very comprehensive solution that you can use on Windows, macOS, or Linux computers.
Is OpenJDK free?
Since this is an open-source initiative, you can download OpenJDK for free and use it without any licensing costs, as the tool is distributed under the GNU General Public License (GPL).
In addition to free usage, you are also free to modify and distribute the software without additional fees. Even though it’s a freemium solution, it doesn’t lack anything in terms of features or capabilities, so it’s perfect for any use case and different scales of projects.
What operating systems are compatible with OpenJDK?
OpenJDK works with many operating systems, including Windows 10 and 11, macOS (10.15 or higher, and it also supports Intel and Apple Silicon chips), and Linux (Ubuntu, Fedora, Debian, and more).
Whatever operating system you’re using to develop your projects, with the Java Virtual Machine’s architecture, you can be sure that your apps will work on other platforms, too, without any code changes.
What are the alternatives to OpenJDK?
Developed by Microsoft, .NET Framework is a full-scale development platform that is mainly used to create applications for Windows, though it has limited support for macOS and Linux, too. You can use different versions of the .NET Framework depending on the Windows version you have, but some editions support even legacy Windows systems. You can use most of the features .NET Framework offers for free, but there might be enterprise-level features or editions that could be paid for. With this tool, you can use languages like C#, F#, and VB.NET, as this solution is an alternative to Java technology. The .NET Framework gives you access to vast and advanced libraries you can use to create a whole range of things, from web services to games.
If you’re looking for an open-source alternative to the .NET framework, then Mono is the choice for you. With this tool, you can develop with C# across Windows, Linux, and macOS, and it gives you access to different .NET APIs that are great for working with game development engines like Unity. The Mono runtime is available for free, and you can expand it with paid third-party tools for debugging or specific enterprise needs.
Java Runtime Environment (JRE) is a subset of the Java programming technology with which you get modules required for running Java applications, like JVM and core libraries. Provided by Oracle, you can use JRE on Windows, macOS, and Linux machines and even more legacy editions of those platforms. JRE helps you make sure that all your Java apps have a consistent environment across those systems. It’s worth keeping in mind, though, that the compiler or debugger is not a part of the Java Runtime Environment, so it isn’t as comprehensive a solution as OpenJDK.
