Counting word frequency using map.merge

Imagine we want to produce a Map with each unique word as a key and it’s frequency as the value.

Prior to Java 8 we would have to do something like this:

Map<String, Integer> map = new HashMap<>();
for(String word : words) {
    if(map.containsKey(word)) {
        int count = map.get(word);
        map.put(word, ++count);
    } else {
        map.put(word, 1);
    }
}

However with the map.merge method we can now do:

Map<String, Integer> map = new HashMap<>();;
for(String word : words) {
    map.merge(word, 1, Integer::sum);
}
return map;

Pretty nice eh?