All Pets Articlesarticles about pets

Here is the problem,when my dog sees another dog he barks and cries because I think he is trying to get close.When he gets close he starts to growl and barks.I take him out for walks everyday and would take him to the dog park every weekend,but I stopped because he was aggressive towards other dogs.He is obedience trained.How can I get him to stop being aggressive?
He is a 11 month old Male German Shepherd.