Elegant way of counting occurrences in a java collection
Check out Guava's Multiset. Pretty much exactly what you're looking for.
Unfortunately it doesn't have an addAll(Iterable iterable) function, but a simple loop over your collection calling add(E e) is easy enough.
EDIT
My mistake, it does indeed have an addAll method - as it must, since it implements Collection.
I know this is an old question, but I've found a more elegant way in Java 8 for counting these votes, hope you like it.
Map<String, Long> map = a.getSomeStringList()
.stream()
.collect(Collectors.groupingBy(
Function.identity(),
Collectors.counting())
);
Any error, just comment.
Now let's try some Java 8 code:
static public Map<String, Integer> toMap(List<String> lst) {
return lst.stream()
.collect(HashMap<String, Integer>::new,
(map, str) -> {
if (!map.containsKey(str)) {
map.put(str, 1);
} else {
map.put(str, map.get(str) + 1);
}
},
HashMap<String, Integer>::putAll);
}
static public Map<String, Integer> toMap(List<String> lst) {
return lst.stream().collect(Collectors.groupingBy(s -> s,
Collectors.counting()));
}
I think this code is more elegant.