Java8: Create HashMap with character count of a String

Question

Wondering is there more simple way than computing the character count of a given string as below?

String word = \"AAABBB\";
    Map ch         


        

Answer 1

     String str = "Hello Manash";
    Map<Character,Long> hm = str.chars().mapToObj(c-> 
    (char)c).collect(Collectors.groupingBy(c->c,Collectors.counting()));
    System.out.println(hm);

Answer 2

Simplest way to count occurrence of each character in a string, with full Unicode support (Java 11+)¹:

String word = "AAABBB";
Map<String, Long> charCount = word.codePoints().mapToObj(Character::toString)
        .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
System.out.println(charCount);

^{1) Java 8 version with full Unicode support is at the end of the answer.}

Output

{A=3, B=3}

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UPDATE: For Java 8+ (doesn't support characters from supplemental planes, e.g. emoji):

Map<String, Long> charCount = IntStream.range(0, word.length())
        .mapToObj(i -> word.substring(i, i + 1))
        .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

---

UPDATE 2: Also for Java 8+.

I was mistaken, thinking that codePoints() wasn't added until Java 9. It was added in Java 8 to the CharSequence interface, so it doesn't show in javadoc for String in Java 8, and shows as added in Java 9 for later versions of the javadoc.

However, the Character.toString​(int codePoint) method wasn't added until Java 11, so to use the Character.toString​(char c) method, we can use chars() in Java 8:

Map<String, Long> charCount = word.chars().mapToObj(c -> Character.toString((char) c))
        .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

Or for full Unicode support, incl. supplemental planes, we can use codePoints() and the String(int[] codePoints, int offset, int count) constructor, in Java 8:

Map<String, Long> charCount = word.codePoints()
        .mapToObj(cp -> new String(new int[] { cp }, 0, 1))
        .collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));

Answer 3

Figured out, below is another simple way.

Map<String, Integer> charCount = new HashMap();
    for(String charr: s.split("")){
        charCount.put(charr,charCount.getOrDefault(charr,0)+1);
}

Answer 4

Hope this help : Java 8 Stream & Collector:

    String word = "AAABBB";
    Map<Character, Integer> charCount = word.chars().boxed().collect(Collectors.toMap(
                    k -> Character.valueOf((char) k.intValue()),
                    v -> 1,
                    Integer::sum));
    System.out.println(charCount);

Output:
    {A=3, B=3}