Count the frequency of words with a HashMap

Description: Count the words of "the cat and the dog and the bird". Print each word with its count, in alphabetical order.

Hint:

• Use a TreeMap (sorted keys) and merge(word, 1, Integer::sum).

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Solution

import java.util.Map;
import java.util.TreeMap;

public class Main {
    public static void main(String[] args) {
        String text = "the cat and the dog and the bird";
        Map<String, Integer> counts = new TreeMap<>();

        for (String word : text.split(" ")) {
            counts.merge(word, 1, Integer::sum);
        }
        counts.forEach((word, n) -> System.out.println(word + " = " + n));
    }
}

How it works

• merge puts 1 if the word is new, or adds 1 to the old count.
• A TreeMap keeps the keys sorted. A HashMap would print them in any order.

Read Java HashMap.

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