Kalyanaraman Santhanam: Edit: Will I encounter any issues if I use add(…) instead of push(…)? Definitly, you will not encounter any issues, because add is part of List interface as well as the Stack, but you should to notice the further readability of your code and your intentions in it by other programmers. push method … Read more
As Evgeny says, the indexer will already replace existing values – so if you just want to unconditionally set the value for a given key, you can do dictionary[key] = value; The more interesting case is the “get a value, or insert it if necessary”. It’s easy to do with an extension method: public static … Read more
There is a hierarchy here: interface IList<T> : ICollection<T> { } interface ICollection<T> : IEnumerable<T> { } You want to aim for the least possible coupling, so return an IEnumerable<T> if that is enough. It probably will be. Return an IList<T> if the situation requires that the caller gets a List that it can use … Read more
java.util.Collections.singleton(object) will give you an immutable Set. singletonList is also available. Less efficiently java.util.Arrays.asList(object) will give you a mutable (can use list.set(0, x);), but non-structurally changeable (can’t add or remove) List. It is a bit more expensive as there is an extra array that is created client-side.
It can be done quite easily using Linq. Convert your list into a new list of pairs (object, original index of object). Sort the new list by the first item in the pair Extract the sorted list and the original indices. Here’s some code to demonstrate the principle: List<int> A = new List<int>() { 3, … Read more
Since Java 8, you can do the following: long[] result = values.stream().mapToLong(l -> l).toArray(); What’s happening here? We convert the List<Long> into a Stream<Long>. We call mapToLong on it to get a LongStream The argument to mapToLong is a ToLongFunction, which has a long as the result type. Because Java automatically unboxes a Long to … Read more
Edit: I just saw you mentioned the String were UK postcodes so I’m fairly confident you couldn’t get very wrong by using a Trove TLongIntHashMap (btw Trove is a small library and it’s very easy to use). Edit 2: Lots of people seem to find this answer interesting so I’m adding some information to it. … Read more
Any collection that you iterate over with foreach may not be modified during iteration. So while you’re running a foreach over rankings, you cannot modify its elements, add new ones or delete any.
Synchronized collections are a waste of time and dangerous. A trivial example why they are bad is to consider two threads running a loop at the same time on the same collection: int i = 0; while (i < list.size()) { if (testSomeCondition(list.get())) { list.remove(i); else i++; } Our list could be synchronized (e.g. a … Read more
I do the former (expose CollectionView from the VM) but what really matters is where your filtering logic is. That should definitely be in the VM so that it can be tested, even if the view has to wire up the CollectionViewSource to the VM. That said, I don’t think there’s anything particularly nasty or … Read more