Apriori algorithm realisation.

Apriori.java

import java.sql.ResultSet;
import java.sql.Statement;

import java.util.StringTokenizer;
import java.util.Vector;

public class Apriori {
    private static Statement stmt;
    private static Vector<String> candidates;
    private static Vector<Double> supports;
    private static double min_support;
    private static double one_percent;


    public static void start(int max_prod_number, double min_supp, Statement new_statement) throws Exception {
        stmt = new_statement;
        min_support = min_supp;
        candidates = null;
        supports = null;
        get_all_transactions();
        for (int i = 1; i <= max_prod_number; i++) {
            generate_candidates(i);
            get_frequent_sets(i);
        }
        prepare_product_data(2);
    }


    public static Vector<String> get_candidates() {
        return candidates;
    }


    public static Vector<Double> get_supports() {
        return supports;
    }


    private static void get_all_transactions() throws Exception {
        String query = "SELECT COUNT(id) FROM bills";
        ResultSet rs = stmt.executeQuery(query);
        rs.next();
        one_percent = rs.getDouble(1) / 100.0;
    }


    private static void prepare_product_data(int count) throws Exception {
        Vector<String> new_candidates = new Vector<String>();

        for (String candidate : candidates) {
            String[] prods;
            if (count > 1)
                prods = candidate.split(" ");
            else
                prods = new String[] {candidate};
            String cnddt = "";
            for (String prod : prods) {
                String query = "SELECT color, consumer, name FROM product_dim WHERE id=" + prod;
                ResultSet rs = stmt.executeQuery(query);
                rs.next();
                cnddt += rs.getString(1) + " " + rs.getString(2)  + " " + rs.getString(3) +",\n";
            }
            new_candidates.add(cnddt.substring(0,cnddt.length()-2));
        }
        
        candidates = new Vector<String>(new_candidates);
    }


    private static void generate_candidates(int count) throws Exception {
        Vector<String> new_candidates = new Vector<String>();

        if (count == 1) { // first set of candidates is loading from db
            String query = "SELECT product FROM facts GROUP BY product";
            ResultSet rs = stmt.executeQuery(query);
            while (rs.next())
                new_candidates.add(rs.getString(1));
        } else if (count == 2) {
            for (int i = 0, candidatesSize = candidates.size(); i < candidatesSize; i++) {
                StringTokenizer st1 = new StringTokenizer(candidates.get(i));
                String str1 = st1.nextToken();
                for (int j = i + 1; j < candidates.size(); j++) {
                    StringTokenizer st2 = new StringTokenizer(candidates.elementAt(j));
                    String str2 = st2.nextToken();
                    new_candidates.add(str1 + " " + str2);
                }
            }
        }

        candidates = new Vector<String>(new_candidates);
    }


    private static void get_frequent_sets(int count) throws Exception {
        Vector<String> new_candidates = new Vector<String>();
        Vector<Double> new_supports = new Vector<Double>();
        for (String candidate : candidates) {
            String query = "";
            if (count == 1) {
                query = "SELECT COUNT(bill) FROM facts WHERE product=" + candidate;
            } else if (count == 2) {
                String[] prods = candidate.split(" ");
                query = "SELECT COUNT(A.bill) " +
                        "FROM facts A, facts B " +
                        "WHERE A.bill=B.bill and " +
                        "A.product=" + prods[0] + " and B.product=" + prods[1];
            }

            ResultSet rs = stmt.executeQuery(query);
            rs.next();
            double support = rs.getDouble(1) / one_percent;
            if (support >= min_support) {
                new_candidates.add(candidate);
                new_supports.add(support);
            }
        }

        candidates = new Vector<String>(new_candidates);
        supports = new Vector<Double>(new_supports);
    }
}