CODEWITHSUNDEEP
javajava-8
Arefe
Arefe

Reputation: 12451

Is there a better way to write using the Java 8 to populate the LinkedHashMap?

I have some code that splits a String of letters, make a List with that and later, populate a LinkedHashMap of Character and Integer with the letter and its frequency. The code is as following, 

   List<String> values = Arrays.asList((subjects.split(",")));
            for (String value : values) {
                char v = value.charAt(0);
                map.put(v, map.containsKey(v) ? map.get(v) + 1 : 1);
            }
            map.put('X', 0);

How can I write it concisely with Java 8 ? Thanks.

Upvotes: 5

Views: 229

Answers (3)

shmosel
shmosel

Reputation: 50746

Try this:

LinkedHashMap<Character, Long> counts = Pattern.compile(",")
        .splitAsStream(subjects)
        .collect(Collectors.groupingBy(
                s -> s.charAt(0),
                LinkedHashMap::new,
                Collectors.counting()));

If you must have an Integer count, you can wrap the counting collector like this:

Collectors.collectingAndThen(Collectors.counting(), Long::intValue)

Another option (thanks @Holger):

Collectors.summingInt(x -> 1)

As a side note, you could replace your looping update with this:

map.merge(v, 1, Integer::sum);

Upvotes: 9

Bohemian
Bohemian

Reputation: 425278

One liner:

Map<String, Long> frequency = Arrays.stream(input.split("(?<=.)\\W*"))
    .collect(Collectors.groupingBy(s -> s, Collectors.counting()));

This counts all "word" characters (letters and digits).

Upvotes: 3

Amir Pashazadeh
Amir Pashazadeh

Reputation: 7322

So you are looking for something like:

Map<Character, Integer> result = new LinkedHashMap<>();
Arrays.asList(subjects.split(""))
      .stream().map(s -> s.charAt(0))
      .forEach(c -> result.put(c, result.containsKey(c) ? result.get(c) + 1 : 1));

and a better solution is

Map<Character, Integer> result = new LinkedHashMap<>();
subjects.chars().mapToObj(c->(char)c)
    .forEach(c -> result.put(c, result.containsKey(c) ? result.get(c) + 1 : 1));

Upvotes: 0

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