How to install JDK sources?
Example for Java 8:
sudo apt-get install openjdk-8-source
apt-get puts it under the relevant JDK location as src.zip: /usr/lib/jvm/java-8-openjdk-amd64/src.zip
Intellij IDEA recognized it automatically and started showing me the source code.
In case of java 11 (on Ubuntu 18.04) I did:
First I install jdk 11:
sudo apt install openjdk-11-jdk
I install the sources like this:
sudo apt-get install openjdk-11-source
And I found them in /usr/lib/jvm/openjdk-11/lib/src.zip
I use Eclipse so I go inside Eclipse's menu Window -> Preferences -> Installed JREs
and inside select
java-11-openjdk-amd64 -> edit -> select the jar (jrt-fs.jar) -> Source Attachment -> External location -> /usr/lib/jvm/openjdk-11/lib/src.zip
Now I happily read the java documentation! :)
Best of luck to all!