J'Lo – the Java Loader

On your machine you rarely need Java 25.0.1+8. You need Java 25 — the newest build.

J'Lo pins major versions and keeps them current: a project's .jlorc holds 25, jlo env installs the newest Eclipse Temurin 25, and once a newer build ships, jlo update replaces it. Nothing in the repo goes stale; the next developer to join gets a working setup.

• Pin the major, not the build — .jlorc says 25, not a build that goes stale
• One build per major — updates replace, they don't pile up
• Found by your tools — JDKs land where IntelliJ IDEA and Gradle toolchains look, JAVA_HOME covers the rest, and J'Lo never deletes or changes a JDK it didn't install
• No shims — jlo exec runs one command with a JDK, for scripts and AI agents
• Single binary; JDKs checked against Adoptium's SHA-256

Linux (x86_64, aarch64) and macOS (arm64), bash ≥ 3.2 and zsh ≥ 5.0.8. Any Java version Temurin builds for your platform — from 8 on Linux, from 11 on macOS.

Installing

Install J'Lo with the install script on Linux and macOS, or with Homebrew on macOS — pick one, not both.

Install Script

/bin/bash -c "$(curl -fsSL https://github.com/java-loader/jlo/releases/latest/download/install.sh)"

The installer ends by printing what to do next: one line to add to your shell profile (plus two optional ones — switching JDK on cd, and tab completion) and the command that loads J'Lo into the shell you are in. It never edits your profile itself.

For upgrades, run jlo selfupdate. Re-running the installer is always safe, and it is the way back should selfupdate ever fail.

Homebrew

On macOS (arm64), J'Lo is also in a Homebrew tap:

brew install java-loader/tap/jlo

Brew prints the profile lines to add; tab completion comes from Homebrew's own setup. Upgrade with brew upgrade jlo — jlo selfupdate is for installer installs only.

Quick Start

jlo env 25        # use Java 25 in this shell, downloading its newest build if needed

For a project:

cd /path/to/your/project
jlo init 25       # write a .jlorc pinning Java 25
jlo env           # use whatever .jlorc says

With the optional autoload line in your profile, cd into the project does the jlo env for you. Autoload never downloads: a pinned JDK that is not installed yet gets a notice, and jlo env fetches it. Outside a project, jlo init --global 25 sets your default — with autoload, every new shell starts on it.

JDKs are installed to ~/Library/Java/JavaVirtualMachines/ on macOS and ~/.jdks/ on Linux, each in a directory named jlo-temurin-<version>. J'Lo never touches anything else in there; jlo list shows it so you can delete it by hand.

A version is a major (25) or a pre-release stream (28-ea). jlo --help lists every command.

Scripts and AI Agents

Your profile makes jlo a shell function, which is what lets jlo env change your current shell. A script, a Makefile or an AI coding agent usually doesn't load your profile, or runs each command in a fresh shell — either way, jlo env has no shell to change. Use exec or home; they work with the plain binary the installer links at ~/.local/bin/jlo:

jlo exec 25 -- ./gradlew build          # one command on Java 25
export JAVA_HOME="$(jlo home 25)"       # just the path

Outside your interactive profile the plain binary still needs ~/.local/bin on PATH; when it is missing, the installer prints the line that adds it. With Homebrew, the binary is on brew's PATH already.

J'Lo puts no java of its own on your PATH. Outside a shell where jlo env ran — by hand or through autoload — java is whatever it was before.

Machine-readable output

jlo list --json and jlo current --json print one JSON document on one line. Keys are only ever added — never removed, renamed or retyped — so ignore keys you do not know, and expect new values in status and source.kind. What J'Lo does not know is null rather than a missing key; the one key that comes and goes is source.path, present only for the two config kinds. On failure the exit status is 1 and stdout is empty — except when writing stdout itself fails, so check the exit status.

jlo list --json | jq -r '.names[] | select(.update) | .name'   # names with an update
jlo current --json | jq -r .version

jlo list --json (--offline composes):

{"names":[{"name":"25","major":25,"distribution":"temurin",
  "installed":[{"version":"25.0.1+8","path":"…/Contents/Home","active":true,"status":"installed"},
               {"version":"25.0.0+36","path":"…/Contents/Home","active":false,"status":"superseded"}],
  "offered":"25.0.2+10","update":true}]}

• names — every name installed or offered, newest major first.
• installed — newest build first; the first is the one the name stands for. path is its JAVA_HOME. active: your JAVA_HOME points into it. status: installed, or superseded by a newer build of the name. active and status are independent: a shell still on an old build is both.
• offered / update — Adoptium's newest build of the name, and whether it is newer than every installed build (false for a name that is only offered, not installed). Both null when J'Lo did not ask: with --offline, or for a pre-release stream whose version has been released. offered: null with update: false: asked, and Adoptium has no build for your machine. If any lookup fails, the command fails rather than print a partial list.

jlo current --json:

{"name":"25","major":25,"distribution":"temurin","version":"25.0.1+8","path":"…/Contents/Home",
 "source":{"kind":"project_config","path":"/home/you/project/.jlorc"},"pinned_elsewhere":null}

• path — JAVA_HOME exactly as set, so compare version, not paths, against jlo list.
• name, major, distribution, version — null when JAVA_HOME is not a JDK J'Lo manages.
• source — why this JDK: kind is project_config or default_config (each with the file's absolute path), newest_installed, or foreign (JAVA_HOME set outside J'Lo); null when nothing accounts for it.
• pinned_elsewhere — null, or {name, major, distribution, source} of a config that asks for a different JDK.

When J'Lo Is the Wrong Tool

• You need a reproducible, exactly pinned JDK — in CI or on a server.
• You need more than a JDK — Maven, Gradle, Node, Python.
• You need a distribution other than Eclipse Temurin.
• You're on Windows, or on a shell other than bash or zsh.

Uninstalling

Remove ~/.jlo/, the ~/.local/bin/jlo symlink and the lines you added to your shell profile. With Homebrew, brew uninstall jlo, then remove the profile lines and ~/.jlo/ (it holds only your jlo init --global default). The JDKs stay in ~/.jdks/ or ~/Library/Java/JavaVirtualMachines/ — delete them too if you no longer need them.