Searching anagrams with Java 8

Question

I have to write program which should be reading file for anagrams and show word + his anagrams. Txt files is very big, after using scanner, listOfWords size is: 25000.

Output example:

word anagram1 anagram2 anagram3 ...
word2 anagram1 anagram2...

I have code, it works but very slow:

  private static List<String> listOfWords = new ArrayList<String>();
  private static List<ArrayList<String>> allAnagrams = new ArrayList<ArrayList<String>>();

  public static void main(String[] args) throws Exception {
    URL url = new URL("www.xxx.pl/textFile.txt");
    Scanner scanner = new Scanner(url.openStream());
    while (scanner.hasNext()) {
      String nextToken = scanner.next();
      listOfWords.add(nextToken);
    }
    scanner.close();

    while (listOfWords.isEmpty() == false) {
      ArrayList<String> anagramy = new ArrayList<String>();
      String wzor = listOfWords.remove(0);
      anagramy.add(wzor);
      char[] ch = wzor.toCharArray();
      Arrays.sort(ch);
      for (int i = 0; i < listOfWords.size(); i++) {
        String slowo = listOfWords.get(i);
        char[] cha = slowo.toCharArray();
        Arrays.sort(cha);
        if (Arrays.equals(ch, cha)) {
          anagramy.add(slowo);
          listOfWords.remove(i);
          i--;
        }
      }
      allAnagrams.add(anagramy);
    }

    for (ArrayList<String> ar : allAnagrams) {
      String result = "";
      if (ar.size() > 1) {
        for (int i = 1; i < ar.size(); i++) {
          result = ar.get(i) + " ";
        }
        System.out.println(ar.get(0) + " " + result);
      }
    }
  }

I have to write it with Java 8 - streams but I don't know. It is possible to use Streams for reading from URL + searching anagrams? Could you help me with searching anagrams by Stream? Teacher told me that code should be shorter that mine with reading a whole list. Only a few lines, is that possible?

Answer 1

You can read the words from the file into a List or directly create a Stream of it:

try (InputStream is = new URL("http://www.someurl.pl/file.txt").openConnection().getInputStream();
     BufferedReader reader = new BufferedReader(new InputStreamReader(is));
     Stream<String> stream = reader.lines()) {
       //do something with stream
}

Then just stream over the list and collect the anagrams, where all words that have the same sorted list of characters are considered anagrams:

Map<String, List<String>> anagrams =
    stream.collect(Collectors.groupingBy(w -> sorted(w)));

The sorted method is just sorting the letters as you did in your example:

public static String sorted(String word) {
    char[] chars = word.toCharArray();
    Arrays.sort(chars);
    return new String(chars);
}