🔀 jdk-switcher

A lightweight command-line tool to switch between multiple installed JDKs using a JSON config file. This utility updates your JAVA_HOME, ensures the selected JDK is in your PATH, and persists the setup via your shell profile.

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⚙️ Setup

1. Install dependencies

You’ll need:

• gcc (typically comes with Xcode or Xcode Command Line Tools)
• cJSON (install via Homebrew: brew install cjson)

2. Build

CJSON_DIR=$(brew --prefix cjson)
gcc -o build/jdk jdk.c -I"$CJSON_DIR/include" -L"$CJSON_DIR/lib" -lcjson

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📁 Configuration

Create a config.json in the same directory as the binary:

{
    "command": "/usr/libexec/java_home -V 2>&1 | sed -nE 's/.* (\/.*)$/\\1/p'",
    "symlink_path": "~/.devtools/jdk",
    "profile_file_path": "~/.zshrc",
    "jdks": [
        "~/Library/Java/JavaVirtualMachines/corretto-21.0.3/Contents/Home",
        "~/Library/Java/JavaVirtualMachines/corretto-17.0.11/Contents/Home",
        "~/Library/Java/JavaVirtualMachines/corretto-11.0.23/Contents/Home",
        "~/Library/Java/JavaVirtualMachines/corretto-1.8.0_412/Contents/Home"
    ]
}

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🚀 Usage

List all configured JDKs

./jdk --list

Switch to a JDK by index

./jdk --use 2

This:

• Creates a symlink at ~/.devtools/jdk pointing to the selected JDK
• Exports it as JAVA_HOME by updating the ~/.zshrc
• Adds it to your PATH (if not already)
• Reloads your shell environment

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💡 Notes

• Only tested with zsh, but should work with any shell that supports sourcing profile files and SIGUSR1 trap.
• If you modify config.json, just re-run ./jdk --use <index> to apply changes.
• The command in config.json is for reference only, one use it to get current available JDKs on mac but still needs to populate the list manually in config.json jdks section.