The problem is that people are really sloppy with terminology. There are 3 important but distinct classes here: O(1) worst-case This is simple – all operations take no more than a constant amount of time in the worst case, and therefore in all cases. Accessing an element of an array is O(1) worst-case. O(1) amortized … Read more
Collections are not generally very useful for DAL returns, because a collection does not implicitly guarantee order. It’s just a bucket of items. An IList, on the other hand, does implicitly guarantee order. So we’re down to IEnumerable or IList. The next question would be: is the List object “live”? i.e., is it connected to … Read more
Edit; I understand this question is getting a lot of hits based on the title so the TLDR for those people is to use the collect() helper to create a Collection instance. In answer to the questioner’s brief: If you have $collection = collect([ (object) [ ‘website’ => ‘twitter’, ‘url’ => ‘twitter.com’ ], (object) [ … Read more
If you want to create a publicly exposed animal collection you should not inherit from List<T> and instead inherit from Collection<T> and use the postfix Collection in the class name. Example: AnimalCollection : Collection<Animal>. This is supported by the framework design guidelines, more specifically: DO NOT use ArrayList, List<T>, Hashtable, or Dictionary<K,V> in public APIs. … Read more
Collection<MyObjectType> myCollection = …; List<MyObjectType> list = new ArrayList<MyObjectType>(myCollection); See the Collections trail in the Java tutorials.
I explained this at the 25-minute point of this video: https://youtu.be/ZeO_J2OcHYM?t=1495 Sorry for the lazy answer, but this is after all only a “why” question (arguably not appropriate to StackOverflow?). EDIT: Here’s another point I’m not sure I made clear in the video: the total (across all of the world’s Java code), amount of extra … Read more
Yes, you understood it correctly. The idea is that the object returned by umodifiableCollection can’t directly be changed, but could change through other means (effectively by changing the internal collection directly). As long as something has access to the internal list, the “unmodifiable” collection could be changed. That’s why you usually construct a unmodifiable collection … Read more
You can create a Stream of the indices using an IntStream and then convert them to a Map : Map<Integer,Item> map = IntStream.range(0,items.size()) .boxed() .collect(Collectors.toMap (i -> i, i -> items.get(i)));
I believe the OP is using a Comparator to partition the input into equivalence classes, and the desired result is a list of members of the equivalence class that is the maximum according to that Comparator. Unfortunately, using int values as a sample problem is a terrible example. All equal int values are fungible, so … Read more
Sounds like you just want: bool hasSameElements = listA.Intersect(listB).Any(); EDIT: As noted in comments, Intersect uses lazy evaluation. It defers all execution until the first element is read from the result; at that point it will load all of listB into a set, and then stream listA until it finds a result to yield. At … Read more