you can check a pokemons happiness in Diamond/pearl by the use of a poketch app, in previous games you could only know in the happiness was maxed by obtain a ribbon from a certain character depending on the game.
Chat with our AI personalities
Go to Vendanturf town Talk to the lady in the house beside "Wanda's House" Note: the Pokemon that you want to check it's happiness must be in front of the line.
get the Poke tech App Poke happyness
Golbat doesn't evolve in pokemon red, blue or yellow. Generation II, and onward, if Golbat's happiness is high enough it will evolve into Crobat.
with raising the Pokemon with that Pokemon for many time You can raise your Pokemon happiness by defeating many trainers with Pokemon do you want to raise.
Maxing out the happiness of a pokemon is somewhat time consuming. Walking around with the pokemon in the lead position will help slowly increase the happiness. You can also feed the pokemon poffins to help raise stats and happiness.