How to Efficiently Count Character Frequency in a String?

Determining Character Frequency in Strings

Counting the frequency of characters in a string is a common task in programming. To achieve this, consider the following question:

Question: How does one efficiently count character frequency in a string?

Answer: To determine character frequency, create a Java Map that maps characters to integers. Iterate through the string's characters and check if they exist in the map. If so, increment their value; otherwise, initialize their value to 1.

Map<Character, Integer> map = new HashMap<>();
String s = "aasjjikkk";

for (int i = 0; i < s.length(); i++) {
    char c = s.charAt(i);
    Integer val = map.get(c);
    if (val != null) {
        map.put(c, val + 1);
    } else {
        map.put(c, 1);
    }
}

This method will result in a map with characters as keys and their respective frequencies as values.

Alternatively, you could utilize Bozho's suggestion of using a Multiset to count character occurrences directly.

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