基于用户、物品做协同过滤

Set<Entry<String, Set<String>>> entrySet = itemUserCollection.entrySet();
        Iterator<Entry<String, Set<String>>> iterator = entrySet.iterator();
        while(iterator.hasNext()){
            Set<String> commonUsers = iterator.next().getValue();
            for (String user_u : commonUsers) {
                for (String user_v : commonUsers) {
                    if(user_u.equals(user_v)){
                        continue;
                    }
                    sparseMatrix[userID.get(user_u)][userID.get(user_v)] += 1;
                    //计算用户u与用户v都有正反馈的物品总数
                }
            }
        }