The JavaDoc files are in the same place as the jar files. So if you are using the latest version of the SDK (version 100.11.0), you can get them from our maven server here:
https://esri.jfrog.io/artifactory/arcgis/com/esri/arcgisruntime/arcgis-java/100.11.0/
We don't publish the source code for the jar files. Even if you cracked it open you are not going to be able to debug very far into the core logic as this is written in C++ and contained in the supplied libraries compiled for the platform you are running on.
- .so files for linux
- .dll for Windows
- .dylib for macOS
The jar you use from us mostly contains JNI interop code.
The reason we write most of our core logic in C++ is that Java isn't the only development platform we support. We also support .Net, Qt (QML), iOS Swift and Android (Kotlin and Java) developers and compiling from our common C++ codebase we can provide a consistent experience on all platforms.
Does this help?