[grimlck]

C++ (Using something like emscripten for the web)

Although, i'd pick java over C++ unless i'm doing some very performance critical

[pjmlp]

While true, it is a pain on Android, given how the Android team treats the C and C++ developers.

The official set of APIs is quite limited and JNI is required for any app that isn't a game.

Even C++ libraries that are wrapped in Java classes, like SKIA, are only accessible via JNI.