AnagramsTogetherLexicographically.java

package com.rampatra.strings;

import java.util.*;

/**
 * Created by IntelliJ IDEA.
 *
 * @author rampatra
 * @since 10/11/15
 */
public class AnagramsTogetherLexicographically {

    /**
     * Takes an array of String {@code strings} and prints anagrams in groups where the groups
     * are arranged lexicographically and the strings within each group are also arranged
     * lexicographically.
     *
     * @param strings
     */
    public static void printAnagramsTogether(String[] strings) {

        HashMap<String, List<Integer>> hashMap = new HashMap<>();
        TreeSet<List<String>> treeSet = new TreeSet<>((Comparator) (o1, o2) -> {
            if (o1 instanceof List<?> && o2 instanceof List<?>) {
                return ((List<String>) o1).get(0).compareTo(((List<String>) o2).get(0));
            } else {
                return 0;
            }
        });

        for (int i = 0; i < strings.length; i++) {
            String spaceRemovedStr = strings[i].replaceAll("\\s+", "");
            char[] chars = spaceRemovedStr.toCharArray();
            Arrays.sort(chars);

            List<Integer> indexes = hashMap.get(String.valueOf(chars));
            if (indexes == null) {
                indexes = new ArrayList<>();
            }
            indexes.add(i);
            hashMap.put(String.valueOf(chars), indexes);
        }

        for (Map.Entry<String, List<Integer>> entry : hashMap.entrySet()) {

            List<String> anagrams = new ArrayList<>();

            for (int i = 0; i < entry.getValue().size(); i++) {
                anagrams.add(strings[entry.getValue().get(i)]);
            }

            Collections.sort(anagrams); // arrange anagrams lexicographically within a single line
            treeSet.add(anagrams); // sort the entire output lexicographically
        }

        treeSet.stream().flatMap(Collection::stream).forEach(System.out::println);
    }

    /**
     * Take list of strings from console and print anagrams in groups.
     *
     * @param args
     */
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        List<String> strings = new ArrayList<>();
        String s;
        System.out.println("Input string in separate lines (blank string to stop):");
        // you should use in.hasNextLine()
        while (!(s = in.nextLine()).trim().equals("")) {
            strings.add(s);
        }
        printAnagramsTogether(strings.toArray(new String[0]));
    }
}