Android - possible way to notify other i chatted using If statement passing in a user?

I wonder how to make an if statement in android studio like if you click the send button it will notify the one i contacted. would that possible in if else? i am creating chat app and i am using firebase as the storage of messages.do you think this would be possible?

if (view == button){
  //number of message
   numMessage++

}
else{

 "notification builder code?"
}

ugh i dunno if what would be the best possible way to notify the other i contacted . because if you set an intent in your send button it will just notify the emulator not the one you send a message. give an idea or any suggestion.