Java count occurrence of each item in an array

List asList = Arrays.asList(array);Set<String> mySet = new HashSet<String>(asList);for(String s: mySet){ System.out.println(s + " " + Collections.frequency(asList,s));}

With java-8, you can do it like this:

String[] array = {"name1","name2","name3","name4", "name5", "name2"};Arrays.stream(array)      .collect(Collectors.groupingBy(s -> s))      .forEach((k, v) -> System.out.println(k+" "+v.size()));

Output:

name5 1name4 1name3 1name2 2name1 1

What it does is:

• Create a Stream<String> from the original array
• Group each element by identity, resulting in a Map<String, List<String>>
• For each key value pair, print the key and the size of the list

If you want to get a Map that contains the number of occurences for each word, it can be done doing:

Map<String, Long> map = Arrays.stream(array)    .collect(Collectors.groupingBy(s -> s, Collectors.counting()));

For more informations:

• Stream
• Collectors

Hope it helps! :)

You could use a MultiSet from Google Collections/Guava or a Bag from Apache Commons.

If you have a collection instead of an array, you can use addAll() to add the entire contents to the above data structure, and then apply the count() method to each value. A SortedMultiSet or SortedBag would give you the items in a defined order.

Google Collections actually has very convenient ways of going from arrays to a SortedMultiset.