jvm - Java Version Manager

A command line tool that helps you install and manage multiple Java versions on your machine.

For now the simplest way to install jvm is to use JBang:

jbang app install jvm@codejive

See:

jvm --help

jvm delegates JDK discovery and installation to the devkitman library. When you request a Java version (e.g. jvm install 17), resolution follows a three-tier cascade:

• 17 — interpreted as 17+, meaning version 17 or newer (open-ended)
• 17! — exact major version 17 only
• temurin-21.0.3 — a provider-specific JDK identifier (matched by ID, not version)

Providers are queried in fixed registration order:

1. current — the JDK running the current process
2. default — the JDK set as the global default (~/.jbang/currentjdk symlink)
3. javahome — the JDK pointed to by JAVA_HOME
4. path — the JDK found on PATH
5. linked — manually linked JDK installations
6. jbang — JBang-managed JDKs (supports install/uninstall)
7. Platform-specific providers (multihome, sdkman, scoop, brew, mise, linux)

The first provider that returns a matching installed JDK wins. There is no cross-provider sorting or "pick the best version" logic — provider priority alone determines the result.

Run jvm list-providers to see which providers are active on your system.

When no installed JDK satisfies the request and the request is open-ended below version 21 (the configured default), the system redirects to version 21 instead of downloading the minimum satisfying version. For example, jvm install 11 (interpreted as 11+) with no local JDKs available will install JDK 21, not 11.

Exact requests bypass this: jvm install 11! will always install exactly version 11.

If the default version itself cannot be resolved (e.g. the download API doesn't offer it), the system aggregates all downloadable JDKs from all installable providers, filters by the original minimum version, and selects the highest available.

• Installed JDKs always take priority over downloads, regardless of version
• Open-ended requests get upgraded to the default version (21) when nothing is installed locally
• Exact requests are honored literally — no version upgrading occurs
• Installation is lazy — resolution may identify a downloadable JDK without downloading it until explicitly needed
• The .jvmrc file in the current directory (or home directory) can specify a default version via java=<version>, used when no version argument is provided

• Java 11+ — required to compile and run (JAVA_HOME must be set)
• Maven — provided via the included wrapper (mvnw / mvnw.cmd), no separate install needed

Full build with formatting and tests:

./mvnw spotless:apply clean verify

Quick build, skipping tests:

./mvnw clean package -DskipTests

The build produces two JARs in target/:

• jvm-<version>.jar — thin JAR (no bundled dependencies)
• jvm-<version>-cli.jar — fat JAR, runnable directly

java -jar target/jvm-<version>-cli.jar --help
java -jar target/jvm-<version>-cli.jar --version
java -jar target/jvm-<version>-cli.jar list

Or use the assembled launcher from target/binary/bin/:

# Linux/macOS
./target/binary/bin/jvm --help
# Windows
target\binary\bin\jvm.bat --help

The project uses Spotless with Google Java Format (AOSP style).

# Apply formatting
./mvnw spotless:apply
# Check without modifying
./mvnw spotless:check

The project supports building native executables using GraalVM. This creates a standalone binary with faster startup time and lower memory footprint.

1. Install GraalVM (recommended: GraalVM 22.3 or later)
2. Set GRAALVM_HOME or JAVA_HOME to point to your GraalVM installation
3. Install the native-image tool:

   gu install native-image

To build a native executable, run:

./mvnw clean package -Pnative

The native executable will be created in target/jvm (or target/jvm.exe on Windows).