Using minHash to compare more than 2 sets

Question

I have a class called FindSimilar which uses minHash to find similarities between 2 sets (and for this goal, it works great). My problem is that I need to compare more than 2 sets, more specifically, I need to compare a given set1 with an unknown amount of other sets. Here is the class:

import java.util.HashSet;
import java.util.Map;
import java.util.Random;
import java.util.Set;

public class FindSimilar<T>
{
private int hash[];
private int numHash;

public FindSimilar(int numHash)
{
    this.numHash = numHash;
    hash = new int[numHash];
    Random r = new Random(11);
    for (int i = 0; i < numHash; i++)
    {
        int a = (int) r.nextInt();
        int b = (int) r.nextInt();
        int c = (int) r.nextInt();
        int x = hash(a * b * c, a, b, c);
        hash[i] = x;
    }
}

public double similarity(Set<T> set1, Set<T> set2)
{
    int numSets = 4;
    Map<T, boolean[]> bitMap = buildBitMap(set1, set2);
    int[][] minHashValues = initializeHashBuckets(numSets, numHash);
    computeFindSimilarForSet(set1, 0, minHashValues, bitMap);
    computeFindSimilarForSet(set2, 1, minHashValues, bitMap);
    return computeSimilarityFromSignatures(minHashValues, numHash);
}

private static int[][] initializeHashBuckets(int numSets,
        int numHashFunctions)
{
    int[][] minHashValues = new int[numSets][numHashFunctions];
    for (int i = 0; i < numSets; i++)
    {
        for (int j = 0; j < numHashFunctions; j++)
        {
            minHashValues[i][j] = Integer.MAX_VALUE;
        }
    }
    return minHashValues;
}

private static double computeSimilarityFromSignatures(
        int[][] minHashValues, int numHashFunctions)
{
    int identicalFindSimilares = 0;
    for (int i = 0; i < numHashFunctions; i++)
    {
        if (minHashValues[0][i] == minHashValues[1][i])
        {
            identicalFindSimilares++;
        }
    }
    return (1.0 * identicalFindSimilares) / numHashFunctions;
}

private static int hash(int x, int a, int b, int c)
{
    int hashValue = (int) ((a * (x >> 4) + b * x + c) & 131071);
    return Math.abs(hashValue);
}

private void computeFindSimilarForSet(Set<T> set, int setIndex,
        int[][] minHashValues, Map<T, boolean[]> bitArray)
{
    int index = 0;
    for (T element : bitArray.keySet())
    {
        /*
         * for every element in the bit array
         */
        for (int i = 0; i < numHash; i++)
        {
            /*
             * for every hash
             */
            if (set.contains(element))
            {
                /*
                 * if the set contains the element
                 */
                int hindex = hash[index];
                if (hindex < minHashValues[setIndex][index])
                {
                    /*
                     * if current hash is smaller than the existing hash in
                     * the slot then replace with the smaller hash value
                     */
                    minHashValues[setIndex][i] = hindex;
                }
            }
        }
        index++;
    }
}

public Map<T, boolean[]> buildBitMap(Set<T> set1, Set<T> set2)
{
    Map<T, boolean[]> bitArray = new HashMap<T, boolean[]>();
    for (T t : set1)
    {
        bitArray.put(t, new boolean[] { true, false });
    }
    for (T t : set2)
    {
        if (bitArray.containsKey(t))
        {
            // item is present in set1
            bitArray.put(t, new boolean[] { true, true });
        }
        else if (!bitArray.containsKey(t))
        {
            // item is not present in set1
            bitArray.put(t, new boolean[] { false, true });
        }
    }
    return bitArray;
}

public static void main(String[] args)
{
    Set<String> set1 = new HashSet<String>();
    set1.add("FRANCISCO");
    set1.add("abc");
    set1.add("SAN");
    Set<String> set2 = new HashSet<String>();
    set2.add("b");
    set2.add("a");
    set2.add("SAN");
    set2.add("USA");
    FindSimilar<String> minHash = new FindSimilar<String>(set1.size() + set2.size());
    System.out.println("Set1 : " + set1);
    System.out.println("Set2 : " + set2);
    System.out.println("Similarity between two sets: "
            + minHash.similarity(set1, set2));
}
}

I need to use the similarity method on more than 2 sets. The problem is that I can't find a way to go over all of them. If I create a for, I can't say I want to compare set1 and seti. I am not sure if I am making sense, I must admit I am a bit confused.

The goal of the program is to compare users. A user has a list of contacts (other users) and similar users have similar contacts. Each set is a user and the contents of the sets will be their contacts.

Answer 1

I have found a (not sure if) cheesy solution for my problem by placing all sets inside an ArrayList structure and then converting it to an actual array:

ArrayList<Set<String>> list = new ArrayList<Set<String>>();

for(int i = 0; i < numPeople; i++){
    Set<String> set1 = new HashSet<String>();
    list.add(set1);
    //another for goes here later on
}

Set<String>[] bs = list.toArray(new Set[0]);

.
.
.

public static void main(String[] args)
{
    .
    .
    .

    for(int i = 1; i<bs.length; i++){
        System.out.format("Set %d: ", i+1);
        System.out.println(bs[0]);
        System.out.println("Similarity between two sets: "
                + minHash.similarity(bs[0], bs[i]));    
    }
}

This gives off a The expression of type Set[] needs unchecked conversion to conform to Set<String>[] warning, but runs fine. This does exactly what I wanted it to (I still need a for to put data inside the sets, but that shouldn't be hard. If anyone could tell me if this solution should be used or if there is a better alternative, I'd like to hear it, since I am still learning and any info would be useful.