Automatic marker zoom

I use this code to retrieve Lat and lang from a user in firebase, My question is how to automatically zoom in on the bookmark ...

mDatabase.child(mPost_key).addValueEventListener(new ValueEventListener() {
               @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            Location childLocation = dataSnapshot.getValue(Location.class);
            LatLng childPos = new LatLng(childLocation.getLat(),childLocation.getLang());
            MarkerOptions markerOptions  =new MarkerOptions().position(childPos);
            Marker marker = mMap.addMarker(markerOptions);
            userMarkers.put(dataSnapshot.getKey(),marker);


               }