WordCountEngine.java

package pramp.string;


import java.util.*;

public class WordCountEngine {

    static String[][] count(String document) {
        Map<String, Integer> map = new HashMap<>();
        String[] tokens = document.toLowerCase().replaceAll("[^a-z ]", "").split("\\s+");
        List<String> list = new ArrayList<>();
        for (String word : tokens) {
            if (map.containsKey(word)) {
                map.put(word, map.get(word) + 1);
            } else {
                map.put(word, 1);
                list.add(word);
            }
        }
        Map<Integer, ArrayList<String>> reducedMap = new TreeMap<>(new Comparator<Integer>() {
            @Override
            public int compare(Integer o1, Integer o2) {
                return o1.compareTo(o2) * -1;
            }
        });
        for (String word : list) {
            if (!reducedMap.containsKey(map.get(word))) {
                reducedMap.put(map.get(word), new ArrayList<>());
            }
            reducedMap.get(map.get(word)).add(word);
        }
        String[][] toBeReturned = new String[list.size()][2];
        int j = 0;
        for (Integer i : reducedMap.keySet()) {
            for (String word : reducedMap.get(i)) {
                toBeReturned[j++] = new String[]{word, String.valueOf(i)};
            }
        }
        return toBeReturned;
    }
}