Java List Sort extractRankedProducts( List<String> unsortedProducts)

Description

Extracts the products which occurred more than once in the unsorted list and sorts them based on their occurrence

License

Open Source License

Parameter

Parameter	Description
unsortedProducts	list of products with out any sorting

Return

products sorted by ranking occurrence and that occurred more than 1 time

Declaration

public static List<String> extractRankedProducts(
        List<String> unsortedProducts)

Method Source Code

//package com.java2s;
//License from project: Open Source License 

import java.util.ArrayList;

import java.util.Collections;
import java.util.Comparator;

import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;

public class Main {
    /**//from w w  w  .  j  ava  2s. co m
     * Extracts the products which occurred more than once in the unsorted list and sorts them
     * based on their occurrence
     * @param unsortedProducts list of products with out any sorting
     * @return products sorted by ranking occurrence and that occurred more than 1 time
     */
    public static List<String> extractRankedProducts(
            List<String> unsortedProducts) {
        final Map<String, Integer> occurencesMap = createOccurrenceMap(unsortedProducts);

        Comparator<String> comparator = new Comparator<String>() {
            @Override
            public int compare(String o1, String o2) {
                Integer occurenceO1 = occurencesMap.get(o1);
                Integer occurenceO2 = occurencesMap.get(o2);
                int comparedOccurence = occurenceO2.compareTo(occurenceO1);
                return comparedOccurence;
            }
        };

        List<String> sortedList = new ArrayList<String>(
                new HashSet<String>(unsortedProducts));
        Collections.sort(sortedList, comparator);

        int i = 0;
        while (i < sortedList.size()) {
            if (occurencesMap.get(sortedList.get(i)) == 1) {
                sortedList.remove(i);
            } else {
                i++;
            }
        }

        return sortedList;
    }

    public static Map<String, Integer> createOccurrenceMap(
            List<String> unsortedProducts) {
        Map<String, Integer> occurencesMap = new HashMap<String, Integer>();

        for (String recommendedItem : unsortedProducts) {
            if (occurencesMap.containsKey(recommendedItem)) {
                occurencesMap.put(recommendedItem,
                        occurencesMap.get(recommendedItem) + 1);
            } else {
                occurencesMap.put(recommendedItem, 1);
            }
        }
        return occurencesMap;
    }
}

Java List Sort extractRankedProducts( List unsortedProducts)