Managing JDKs in MacOS

With the increasing number of JDK builds and the more frequent release cadence, I found it hard to keep track what I had installed in my MacOS and switch between them on the fly.

Even in 2020 my preferred version of Java is 1.8(although I am trying to make use of Java 14 as much as possible), probably because this is the version I am using at my work. But depending on the occasion I find myself experimenting with newer features from later versions, or even from experimental builds:

• JShell from Java 9 onwards
• EpsilonGC
• The use of var since Java 10
• Value types in Project Valhalla builds
• ZGC (the key feature I want to start making use of Java14)
• etc…

In addition, nowadays on my personal computer I mainly use Java builds from the AdoptOpenJDK project. But there are other builds which I have installed on my MacOS to try out:

• GraalVM
• Zulu
• Coretto

Hence I spent some putting together some bash functions that give me a hand managing and switching between those versions on the fly.

For the complete bash script see here, but the highlights are:

List JKDs

function listJDKs() {
    echo "$($java_home -V 2>&1)"
}

Output

[:~]$listJDKs
Matching Java Virtual Machines (5):
    14, x86_64: "AdoptOpenJDK 14"   /Library/Java/JavaVirtualMachines/adoptopenjdk-14.jdk/Contents/Home
    13.0.2, x86_64: "AdoptOpenJDK 13"   /Library/Java/JavaVirtualMachines/adoptopenjdk-13.jdk/Contents/Home
    1.8.0_222, x86_64:  "AdoptOpenJDK 8"    /Library/Java/JavaVirtualMachines/adoptopenjdk-8.jdk/Contents/Home
    1.8.0_212, x86_64:  "GraalVM CE 19.0.0" /Library/Java/JavaVirtualMachines/graalvm-ce-19.0.0/Contents/Home
    1.8.0_163-zulu-8.28.0.1, x86_64:    "Zulu 8"    /Library/Java/JavaVirtualMachines/zulu-8.jdk/Contents/Home

List Different JDK builds

function listJDKVendors() {
    echo "$($java_home -V 2>&1 | tr ' ' '\0' | tr '\t' ' ' | cut -d ' ' -f2,1)"
}

Output

[:~]$listJDKVendors
MatchingJavaVirtualMachines(5):
14,x86_64: "AdoptOpenJDK14"
13.0.2,x86_64: "AdoptOpenJDK13"
1.8.0_222,x86_64: "AdoptOpenJDK8"
1.8.0_212,x86_64: "GraalVMCE19.0.0"
1.8.0_163-zulu-8.28.0.1,x86_64: "Zulu8"

Set JDK to a specific version/vendor

function setJDK() {

    local USAGE="Usage: setJDK [-v \${JDK_VERSION}] [-d \${JDK_DISTRIBUTION}]"

    local OPTIND v d
    while getopts "v:d:" OPTION; do
        case "$OPTION" in
            v)
                local version=$OPTARG
                ;;
            d)
                local dist=$OPTARG
                ;;
            ?)
                echo $USAGE
                return 1
                ;;
        esac
    done

    if [ $# -lt 1 ]; then
        echo $USAGE
        return 1
    fi

    if [ -n "$version" ] && [ "$dist" ]; then
        echo "Setting JAVA to version $version and distribution $dist"
        local versionAndDistNo=$($java_home -V 2>&1 | grep $dist | grep $version | wc -l)
        if [ "$versionAndDistNo" -gt 1 ];then
            echo "Multiple JAVA versions found for arguments -v $version -d $dist . Unable to setJDK"
            listJDKs
            return 1
        else
            export JAVA_HOME=$($java_home -V 2>&1 | grep $dist | grep $version | tr ' ' '\0' | tr '\t' ' ' | cut -d ' ' -f 3)
        fi
    elif [ -n "$dist" ]; then
        echo "Setting JAVA to distribution $dist"
        local distNo=$($java_home -V 2>&1 | grep $dist | wc -l)
        if [ $distNo -gt 1 ];then
            echo "Multiple versions for $dist. Unable to setJDK"
            listJDKs
            return 1
        else
            export JAVA_HOME=$($java_home -V 2>&1 | grep $dist | tr ' ' '\0' | tr '\t' ' ' | cut -d ' ' -f 3)
        fi
    elif [ -n "$version" ]; then
        echo "Setting JAVA to version $version"
        export JAVA_HOME=$($java_home -v $version)
    else
        echo $USAGE
    fi

    echo "JAVA_HOME=${JAVA_HOME}"
    return 0
}

Output

[:~]setJDK -v 14
Setting JAVA to version 14
JAVA_HOME=/Library/Java/JavaVirtualMachines/adoptopenjdk-14.jdk/Contents/Home

Note that java_home=/usr/libexec/java_home

Comments

[philippsuntz]

Hi Nikos,

nice article. I had to same, needing to change my JDK for multiple projects with a new developed and a legacy code base. For me i found sdkman very helpful (sdkman.io/).
It dose the same job as your script + it allows you to download additional JDKs if needed. Also tools like gradle can be managed with it and maintained in multiple versions.

[Nikos Katsanos]

Hey Philip, Thank you for the suggestion. Didn't know about that, but it looks pretty cool and promising. Will give it a go. I definitely prefer something that is supported by many people :)

[Rémi Lavedrine]

Hi Nikos,

I encountered this problem using an SDK for iOS application obfuscation.
I used jenv and it works pretty well.

[Nikos Katsanos]

Hello Rèmi, thank you for suggesting. Seems like managing JDKs in a Mac/Dev machine is a general concern. jevn looks promising as well. Pretty sure this and http:// sdkman.io as suggested above will be much better than my hacky scripts :)

[Rémi Lavedrine]

I explained how I made it in that Post :

Application Obfuscation on iOS

Rémi Lavedrine ・ Jun 27 '19 ・ 7 min read

#security #ios

It is basically :

brew install jenv
echo 'export PATH="$HOME/.jenv/bin:$PATH"' >> ~/.bash_profile
echo 'eval "$(jenv init -)"' >> ~/.bash_profile
source ~/.bash_profile