Get app's storage path without context

Service itself is a context http://developer.android.com/reference/android/app/Service.html you can use.

this.getExternalFilesDir()

on the service.

Prior to Android 6 & prior to forced scoped storage, the following would work with Android 5.

String path = Environment.getExternalStorageDirectory().getAbsolutePath();

This answer no longer works on Android 11 and in 2020.