Eclipse Temurin 21 JDK

Eclipse Temurin 21 is the Eclipse Adoptium distribution of the OpenJDK 21 Java development kit. It supplies a Java runtime and development tools for building and running Java 21 applications, services, and build pipelines. Java developers, students, and teams maintaining Java 21 deployments can use it without purchasing an Oracle Java subscription.

Main features

• Compile Java with javac, run applications with the HotSpot JVM, and package code with jar.
• Use the Java 21 standard libraries, language capabilities, and long-term-support update line.
• Diagnose running programs with JDK tools, including jcmd, jstack, and Java Flight Recorder.
• Obtain tested binaries through Adoptium, with Java compatibility testing and the AQAvit quality suite.
• Install a native Mac package or choose separate builds for other supported operating systems.

Installation and first use

Install brew install --cask temurin@21. Homebrew uses the official macOS PKG installer, which may require administrator authorization. The JDK is installed under /Library/Java/JavaVirtualMachines/temurin-21.jdk/Contents/Home, rather than as a graphical application in Applications. Select this JDK in your IDE or configure JAVA_HOME using /usr/libexec/java_home -v 21; check java -version and javac -version to ensure the intended Java version is active.

Requirements, dependencies, and conflicts

Separate native macOS packages are provided for Apple Silicon (aarch64) and Intel (x64). Adoptium's current Java 21 support matrix lists macOS 12, 13, 14, and 15 for both architectures. The Homebrew snapshot includes Big Sur and newer variations but declares no explicit macOS minimum; this is not equivalent to the vendor's tested support matrix. Consult the vendor matrix for support guarantees.

The Homebrew cask declares no additional formula dependencies and no explicit cask conflicts. Other major-version JDKs can be installed in separate directories, but JAVA_HOME, PATH, and your IDE determine which JDK is used; the same Temurin 21 installer receipt should not be independently managed by multiple installers. Maven, Gradle, and IDEs are optional separate tools with their own Java-version requirements.

Beyond this Mac-only cask, Adoptium provides Java 21 packages for supported Windows, Linux and AIX targets. The retrieved Java21 matrix includes Windows x64 and Windows aarch64, as well as multiple Linux architectures; support for a particular OS version and architecture must be checked separately. Android and iOS are not ordinary desktop Temurin JDK installation targets. Package formats and native dependencies vary by system; a Mac PKG cannot be installed on Windows or Linux. The published platform matrix is a tested-support list, not proof of one universal binary minimum.

Hardware needs depend on heap size, projects, build tools and application workloads; no universal RAM/storage minimum is specified in the linked installer guide. The cask installs a system JDK, not a graphical IDE. Use a current patch of the Java21 line for maintenance/security fixes; Java21's language/runtime baseline is distinct from an individual patch release. Java21 supports capabilities such as virtual threads, but patch updates are not new major Java language releases.

Accounts, costs, and license

Downloading and using Temurin requires no Adoptium account or subscription and the binaries are free, including commercial use. Third-party paid support arrangements are separate. OpenJDK is distributed under GNU GPL version 2 with the Classpath Exception; bundled components have their own notices. Eclipse Adoptium and its contributors maintain the distribution.

References: Temurin, macOS installation, supported platforms, OpenJDK 21 source, and official Temurin builds.

Historical engineering workflow

The official Adoptium January 26, 2024 release article supplies a Jenkins console image verifying reproducibility of Temurin 21.0.2+13 on Linux ARM64. This is a real historical Temurin 21 engineering-verification workflow, not a Mac installer, graphical Java application or capture of the current 21.0.12.1 package. Platform and release differences are retained.