In the Android SDK, the @hide annotation is only used when building the version of the android.jar stub. At compilation, time characters are imported from this stub, and only non-hidden characters are available. At run time, in a device or emulator, characters are present in platform libraries and can be seen, for example, by reflection.
If your SDK consists only of a jar file or something similar, there really is no way to hide the characters in it.
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