How to open Javadoc JAR file in web browser
- Rename the file akka-persistence-spanner_2.13-1.0.0.0-RC13-javadoc.jar to akka-persistence-spanner_2.13-1.0.0.0-RC13-javadoc.zip
- Use your favourite unzip tool (WinRAR / WinZIP) to extract it, now you have a folder akka-persistence-spanner_2.13-1.0.0.0-RC13-javadoc
- Double click index.html will open the index page on your default web browser.
How to generate Javadoc from a source JAR?
Running the command javadoc:
javadoc --ignore-source-errors -encoding UTF-8 -sourcepath "akka-persistence-spanner_2.13-1.0.0.0-RC13-sources.jar" -d "akka-persistence-spanner_2.13-1.0.0.0-RC13-javadoc" -subpackages 
