How to achieve security for services programmatically, in such a way that yo ur service should not get triggered from outside applications?

Answer: Don't give any intent-filters for your service tag [or] put exported="false" in service
tag [or] LocalServiceManager

Description :
If you don't want to expose your service to outside apps, 3 ways are there. 1. Don't give intent-fiiter tag, so that outsiders can't specify intent action to trigger your service. or 2. User exported="false" in service tag, so that outside world cant trigger it. or 3. User local service manager.