We are developing android native app using java i am not able to find any related document of implementation for native android app.
CesiumJS is a JavaScript, so if you want to integrate it into an Android app you might have to use a WebView or something like that that can run HTML/JavaScript in your Android app. After that it’ll be just like writing a web app and all the documentation/tutorials on cesiumjs.org should apply.
We don’t have any official support for integrating with native Android apps as far as I’m aware.
Cordova is also a good ways to get started. We have a (slighter older, admittedly) blog post on creating an Android app with Cordova.