the quickest way to Implement an algorithm to count how many times each string is present in an array of strings using Java

Question

Just wondering what the quickest way to Implement an algorithm to count how many times each string is present in an array of strings using Java would be?

this is what i have tried and it works but im worried it might be "cheating" as it strays away from the question a bit:

{
    String[] stringArray = {"Random", "Words", "Here","Random", "Words", "Here","Random", "Words", "Here","Random", "Words", "Here"};

    List asList = Arrays.asList(stringArray);
    Set<String> mySet = new HashSet<>(asList);

    mySet.stream().forEach((s) -> {
        System.out.println(s + " " +Collections.frequency(asList,s));
    });
}

Answer 1

The easiest way is to use Map#merge() :

Map<String, Integer> m = new HashMap<>();
for (String s : array)
    m.merge(s, 1, Integer::sum);

after that, m will hold strings as keys and occurrences as values:

m.forEach((k, v) -> System.out.format("%s occured %s time(s)\n", k, v));

Answer 2

By using Collectors in streams:

Arrays.stream(list).collect(Collectors.groupingBy(e -> e, Collectors.counting()))

So, if you have something like this:

        String[] list = new String[4];
        list[0] = "something";
        list[1] = "gfddfgdfg";
        list[2] = "something";
        list[3] = "somet444hing";
        System.out.println(Arrays.stream(list).collect(Collectors.groupingBy(e -> e, Collectors.counting())));

output will be:

{gfddfgdfg=1, something=2, somet444hing=1}

Answer 3

I would use the groupingBy to return a map of counts.

Map<String, Long> counts = Stream.of(array)
                           .collect(Collectors.groupingBy(w -> w, Collectors.counting()));

to print these as well you can do

Stream.of(array)
      .collect(Collectors.groupingBy(w -> w, Collectors.counting()))
      .forEach((k, v) -> System.out.println(k + " occurred " + v " times));