This code is trying to implement a friend recommendation algorithm by using Hadoop mapreduce. The details can be found in Stanford Course CS 246, 2014 HW1. Each line in the input text file (http://snap.stanford.edu/class/cs246-data/hw1q1.zip) records UserID<tab>FriendID where FriendID is a list of user's friend separated by comma. The algorithm will recommend 10 users with most common friends outside the friendlist for each UserID with a format UserID<tab>RecommendFriendID where RecommendFriendID is a list of recommended UserID separated by comma. The recommended UserID will be in a decreasing order of the number of mutual friends. If there are recommended users with the same number of mutual friends, then output those user IDs in numerically ascending order.