Question

I recently came across a module in my application which heavily uses Collections and Lists. And yeah its in Java. So either for performance reasons or whatsoever the author has used Lists and also maps in so many places. He does the usual operations on it like deleting some elements, adding, updating the list and every time he does that, he does it by traversing the entire list. Some times the lists are in the range of 10,000 elements.

Now my question here is why there isnt a language feature which facilitates this operation ? I mean why cant we have some rudimentary SQL which can be performed on the lists and collections ?? Is there any language which has this kind of feature ?

P.S: Well, I am not sure whether this is a bit subjective and against the SO rules. But I am strongly tempted to ask this here. May be the admins can place it right. So here goes.

Answer 1

Along with Google Collections, I’d recommend looking at LambdaJ:

List<Person> sortedByAgePersons = new ArrayList<Person>(persons);
Collections.sort(sortedByAgePersons, new Comparator<Person>() {
        public int compare(Person p1, Person p2) {
           return Integer.valueOf(p1.getAge()).compareTo(p2.getAge());
        }
});

becomes

List<Person> sortedByAgePersons = sort(persons, on(Person.class).getAge());

Lots of neat sorting, filtering and list manipulation functions.