I\'m using reflection method freeStorageAndNotify:
Method freeStorageAndNotify = null;
freeStorageAndNotify = service.packageManager.getClass().getMethod(
Refer to these pages: permissions by protection level and protection level definitions.
android.permission.CLEAR_APP_CACHE
This falls under the protection level "signature|privileged" which means that only same-signature or privileged apps (system signed basically) can have this permission.
Also you should check out the Behavior Changes in general.