Calculating frequency of each word in a sentence in java

Question

I am writing a very basic java program that calculates frequency of each word in a sentence so far i managed to do this much

import java.io.*;

class Linked         


        

Answer 1

Use a map with word as a key and count as value, somthing like this

    Map<String, Integer> map = new HashMap<>();
    for (String w : words) {
        Integer n = map.get(w);
        n = (n == null) ? 1 : ++n;
        map.put(w, n);
    }

if you are not allowed to use java.util then you can sort arr using some sorting algoritm and do this

    String[] words = new String[arr.length];
    int[] counts = new int[arr.length];
    words[0] = words[0];
    counts[0] = 1;
    for (int i = 1, j = 0; i < arr.length; i++) {
        if (words[j].equals(arr[i])) {
            counts[j]++;
        } else {
            j++;
            words[j] = arr[i];
            counts[j] = 1;
        }
    }

An interesting solution with ConcurrentHashMap since Java 8

    ConcurrentMap<String, Integer> m = new ConcurrentHashMap<>();
    m.compute("x", (k, v) -> v == null ? 1 : v + 1);