TeaVM maven plugin 0.6.1 : Unexpected error occurred: Unsupported class file major version 62

 [ERROR] Failed to execute goal org.teavm:teavm-maven-plugin:0.6.1:compile (web-client)
 on project github-browser: Unexpected error occurred: Unsupported class file major
 version 62 -> [Help 1]

This happens if Maven mistakenly points to java version greater than Java 11. This happens on most of the java versions which are greater than 11 Check java home:

mvn --version

Apache Maven 3.6.3 (cecedd343002696d0abb50b32b541b8a6ba2883f)
Maven home: /home/USERNAME/.maven-bin/apache-maven-3.6.3
Java version: 18.0.1, vendor: Oracle Corporation, runtime: /usr/lib/jvm/jdk-18.0.1
Default locale: en_US, platform encoding: UTF-8
OS name: “linux”, version: “5.13.0-27-generic”, arch: “amd64”, family: “unix”

Lets downgrade /usr/lib/jvm/jdk-18.0.1 to jdk 11 using Jenv (Java Environment Manager) and still keep both of the jdk 18 and 11.

---

Managing multiple JVM versions with Jenv:

Jenv can manage multiple Java verions similar to NodeJS verions manager nvm except you have to download each JDK versions yourself and link them with Jenv like:

jenv add JDK_PATH 

command. then linked Java verions can be displayed with jenv versions command:

jenv versions 

should display:

system
  11
  11.0
  11.0.1
  openjdk64-11.0.1
  1.8
  1.8.0.191
  oracle64-1.8.0.191
  18
  18.0
  18.0.1
  openjdk64-18.0.1

Now jenv global command should set current Java versions like:

jenv global oracle64-1.8.0.191 

should select Oracle JDK as current Java verion:

system
  11
  11.0
  11.0.1
  openjdk64-11.0.1
  1.8
  1.8.0.191
* oracle64-1.8.0.191 (set by /home/mohi/.jenv/version)
  18
  18.0
  18.0.1
  openjdk64-18.0.1

---

Now, to address TeaVMs java verions issues we are going to have both JDK 11 and newer Java verion installed on the system and maintain via Jenv:

#dowload jdk 11
cd ~
wget https://mirrors.huaweicloud.com/openjdk/11.0.1/openjdk-11.0.1_linux-x64_bin.tar.gz

#extract
tar -zxvf openjdk-11.0.1_linux-x64_bin.tar.gz

#install Jenv (Java environment Manager)
git clone https://github.com/jenv/jenv.git ~/.jenv
echo 'export PATH="$HOME/.jenv/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(jenv init -)"' >> ~/.bashrc

#Restart terminal and run:
jenv enable-plugin export
exec $SHELL -l

Restart terminal again and check installation:

jenv --version

Should display:

jenv 0.5.5

Now add JDK 11 into Jenv:

jenv add ~/jdk-11.0.1

To check jdk version run:

jenv versions

should display:

system
  11
  11.0
  11.0.1
  openjdk64-11.0.1
  18
  18.0
  18.0.1
  openjdk64-18.0.1

Now select Java version to 11:

jenv global openjdk64-11.0.1

Check selected java version:

jenv versions

Should display:

  system
  11
  11.0
  11.0.1
* openjdk64-11.0.1 (set by /home/USERNAME/.jenv/version)
  18
  18.0
  18.0.1
  openjdk64-18.0.1

Check JAVA_HOME,java and javac version:

echo $JAVA_HOME

/home/USERNAME/.jenv/versions/openjdk64-11.0.1

java --version

openjdk 11.0.1 2018-10-16
OpenJDK Runtime Environment 18.9 (build 11.0.1+13)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.1+13, mixed mode)

javac --version

javac 11.0.1

mvn --version

Apache Maven 3.6.3 (cecedd343002696d0abb50b32b541b8a6ba2883f)
Maven home: /home/USERNAME/.maven-bin/apache-maven-3.6.3
Java version: 11.0.1, vendor: Oracle Corporation, runtime: /home/USERNAME/jdk-11.0.1
Default locale: en_US, platform encoding: UTF-8
OS name: “linux”, version: “5.13.0-27-generic”, arch: “amd64”, family: “unix”