Newbie distributed computing question

I am interested in distributed computing but new to this field. Now I have a question regarding to this field. My question is `how can I programm to compute and find the occurrence of a great deal of integers?' For instance, suppose there 1m integers, in which there are several integer which may repeat, e.g., ... 2, 2, .... 999 ... 999 ...; therefore, what I would like to do is to

count how many times those integers occur.

I understand there has some frameworks, e.g., Hadoop, which can help to deal with such kind of task. But what I would like is to go through some explain and learn some important issues related to distributed computing through a simple example.

Is there any example/ tutorial that may have such kind of explain? Or any resource/book may talk about this?

I appreciate any suggestion.

Thank you very much.