Unless your fruit trees are well lestablished, it's usually a good idea to thin fruits off a young fruit tree. My Rubinette apple, which is going through it's 2nd year in ground put out a fair amount of apples this year.
As much as I would love to try to keep every single apple on my young tree. The quality of fruit would not be as good and the thin branches would not be able to support the weight of the full size apples. It's already struggling as is with the small immature fruit. I'm afraid that it will eventually break my scaffolding limbs if I left them all on the tree.
This quick video shows how I choose which ones to pluck off.