findJavaRuntimes should search in more paths

[rubensa]

Suggestion

When looking for existing Java Runtimes, findJavaRuntime.ts should search in more paths than currently is doing.

At least it should look for the paths specified in java.configuration.runtimes settings variable (as those are already known runtimes).

It also would be great to look if known tools like SDKMan are installed and search their installation paths ($SDKMAN_DIR/candidates/java if SDKMAN_DIR env variable is defined or $HOME/.sdkman/candidates/java if not)

Use Cases

I'd like that the Installed JDKs tab from Configure Java Runtime view shows my installed JDKs.

Examples

Currently I have VSCode with Remote Development extension using a Docker container where I have installed multiple Java versions using SDKMan but only the one pointed by JAVA_HOME (that is set by SDKMan) is listed despite I have manually listed them all under java.configuration.runtimes.

Workaround

As a workaround I had to sym-link $SDKMAN_DIR/candidates/java to /usr/lib/jvm so my installed JDKs are listed.

[testforstephen]

Take a look at jEnv as well.

[achaphiv]

The current behavior doesn't work when running via flatpak.

It would help to either:

• Expose an environment variable to override /usr/lib/jvm
• Also check /usr/lib/sdk/** (and its unique structure) by default

More context at: redhat-developer/vscode-java#510

[Eskibear]

To systematically resolve this issue, I'm planning to make findJavaRuntime.ts a shared lib. This lib will possibly cover jdks installed by below tools:

• sdkman
• asdf
• flatpak

let me know if there's other popular package manager/installer you want me to cover.

[Eskibear]

now use jdk-utils for more coverage.