JDKs and IDEs Tips & FAQ

Running Multiple JDKs

Ref: https://gist.github.com/brightzheng100/20bd34c37367219340bdb359040370dd#file-multi-java-version-support-md

To support multiple Java version, with ZSH:

1. Pick The Right JDKs with Right Versions

For example, we're going to have two JDKs, v8 and v11, with HotSpot installed.

$ export JDK8=adoptopenjdk8
$ export JDK11=adoptopenjdk11

Or if OpenJDK with OpenJ9 (instead of HotSpot)

$ export JDK8=adoptopenjdk8-openj9
$ export JDK11=adoptopenjdk11-openj9

Note: check the available versions here

2. Install Multiple Java Versions:

$ brew cask install ${JDK8}
$ brew cask install ${JDK11}

3. Make then switchable, with a default version:

$ cat <<EOF >> ~/.zshrc
# Multiple Java Versions
export JAVA_8_HOME=$(/usr/libexec/java_home -v1.8)
export JAVA_11_HOME=$(/usr/libexec/java_home -v11)

alias java8='export JAVA_HOME=$JAVA_8_HOME'
alias java11='export JAVA_HOME=$JAVA_11_HOME'

#default java11
export JAVA_HOME=$JAVA_11_HOME
EOF

Now, to switch versions, do this:

$ java8
$ java -version
openjdk version "1.8.0_232"
OpenJDK Runtime Environment (AdoptOpenJDK)(build 1.8.0_232-b09)
OpenJDK 64-Bit Server VM (AdoptOpenJDK)(build 25.232-b09, mixed mode)

$ java11
$ java -version
openjdk version "11.0.4" 2019-07-16
OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.4+11)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.4+11, mixed mode)

Note: as the process has nothing special, you may simply do it in ~/.bash_profile too with pure Bash env

IDE Failed To Start: failed to create java virtual machine.

Ref: https://gist.github.com/brightzheng100/20bd34c37367219340bdb359040370dd#file-sts-failed-to-start-md

Sometimes STS/Eclipse failed to start: failed to create java virtual machine.

It might be caused by multiple JDKs installed.

So we have to specify if it helps.

$ sudo vi /Applications/STS.app/Contents/Eclipse/STS.ini
...
-vm
/Library/Java/JavaVirtualMachines/adoptopenjdk-8.jdk/Contents/Home/bin/java
-vmargs
...

Note: -vm must be before -vmargs!

IDE with lombok support

Project Lombok is cool, but it's not installed by default for most of the IDEs. So a simple installation process might be required.

For STS/Eclipse

1. We may download the lombok.jar from here, or use the one in your ~/.m2/repository/org/projectlombok/ folder;
2. Run java -jar <THE-PATH-TO-YOUR-JAR>;

3. It will prompt up an UI for you to pick up what IDEs (e.g. Eclipse, STS) to install for, choose yours;

4. Click install button and it's done.

Note: for STS/Eclipse, it will actually copy the jar file to IDE's folder and update its .ini file. For example, it adds below in /Applications/STS.app/Contents/Eclipse/STS.ini file:

...
-javaagent:/Applications/STS.app/Contents/Eclipse/lombok.jar

For VS Code

There is an addon we can install to make VS Code have lombok support. Search this addon by keyword lombok will do.