function class_version --argument-names class_file

    if not string match -q '*.class' "$class_file"
        echo "Expected a Java class file but got: $class_file"
        return 1
    end

    # Use the `file` command if available
    if command -q file
        command file "$class_file"
        return 0
    end

    javap -verbose "$class_file" | string match -rq 'major version: (?<major_version>\d+)'

    set -l version_name

    # https://en.wikipedia.org/wiki/Java_class_file#General_layout
    switch "$major_version"
        case 65
            set version_name 'Java SE 21'
        case 64
            set version_name 'Java SE 20'
        case 63
            set version_name 'Java SE 19'
        case 62
            set version_name 'Java SE 18'
        case 61
            set version_name 'Java SE 17'
        case 60
            set version_name 'Java SE 16'
        case 59
            set version_name 'Java SE 15'
        case 58
            set version_name 'Java SE 14'
        case 57
            set version_name 'Java SE 13'
        case 56
            set version_name 'Java SE 12'
        case 55
            set version_name 'Java SE 11'
        case 54
            set version_name 'Java SE 10'
        case 53
            set version_name 'Java SE 9'
        case 52
            set version_name 'Java SE 8'
        case 51
            set version_name 'Java SE 7'
        case 50
            set version_name 'Java SE 6.0'
        case 49
            set version_name 'Java SE 5.0'
        case 48
            set version_name 'JDK 1.4'
        case 47
            set version_name 'JDK 1.3'
        case 46
            set version_name 'JDK 1.2'
        case 45
            set version_name 'JDK 1.1'
        case '*'
            set version_name 'Unknown Java version'
    end

    echo "$version_name (major version $major_version)"
end