For HashSet<T>, the name is UnionWith. This is to indicate the distinct way the HashSet works. You cannot safely Add a set of random elements to it like in Collections, some elements may naturally evaporate. I think that UnionWith takes its name after “merging with another HashSet“, however, there’s an overload for IEnumerable<T> too.
Yes like this: defaultdict(lambda: defaultdict(int)) The argument of a defaultdict (in this case is lambda: defaultdict(int)) will be called when you try to access a key that doesn’t exist. The return value of it will be set as the new value of this key, which means in our case the value of d[Key_doesnt_exist] will be … Read more
As mentioned by others, the reason why get(), etc. is not generic because the key of the entry you are retrieving does not have to be the same type as the object that you pass in to get(); the specification of the method only requires that they be equal. This follows from how the equals() … Read more
Collections.sort(testList); Collections.reverse(testList); That will do what you want. Remember to import Collections though! Here is the documentation for Collections.
See documentation List.Exists (Object method – MSDN) Determines whether the List(T) contains elements that match the conditions defined by the specified predicate. This exists since .NET 2.0, so before LINQ. Meant to be used with the Predicate delegate, but lambda expressions are backward compatible. Also, just List has this (not even IList) IEnumerable.Any (Extension method … Read more
Empty collection. Always. This sucks: if(myInstance.CollectionProperty != null) { foreach(var item in myInstance.CollectionProperty) /* arrgh */ } It is considered a best practice to NEVER return null when returning a collection or enumerable. ALWAYS return an empty enumerable/collection. It prevents the aforementioned nonsense, and prevents your car getting egged by co-workers and users of your … Read more
In JDK 8+, without using any additional libs: Iterator<T> source = …; List<T> target = new ArrayList<>(); source.forEachRemaining(target::add); Edit: The above one is for Iterator. If you are dealing with Iterable, iterable.forEach(target::add);
Now there is a shorter way with Java 8 using Map::merge. myMap.merge(key, 1, Integer::sum) What it does: if key do not exists, put 1 as value otherwise sum 1 to the value linked to key More information here.
What you are doing may be the simplest way, provided your stream stays sequential—otherwise you will have to put a call to sequential() before forEach. [later edit: the reason the call to sequential() is necessary is that the code as it stands (forEach(targetLongList::add)) would be racy if the stream was parallel. Even then, it will … Read more
Attention: Please see Leo Dabus’ answer for a proper implementation for Swift 4 and Swift 5. Swift 4 or later The Substring type was introduced in Swift 4 to make substrings faster and more efficient by sharing storage with the original string, so that’s what the subscript functions should return. Try it out here extension … Read more