There are several different options, depending on what you mean. If you mean by “value” key-value pair, then you can use something like myMap.exists(_ == (“fish”,3)) myMap.exists(_ == “fish” -> 3) If you mean value of the key-value pair, then you can myMap.values.exists(_ == 3) myMap.exists(_._2 == 3) If you wanted to just test the … Read more
Nobody’s put this up here yet, so I’ll do it! Tthis is now officially supported in Objective-C. As of Xcode 7, you can use the following syntax: NSArray<MyClass *> *myArray = @[[MyClass new], [MyClass new]]; Note It’s important to note that these are compiler warnings only and you can technically still insert any object into … Read more
Here’s the solution: CollectionChanged events on ReadOnlyObservableCollection You have to cast the collection to INotifyCollectionChanged.
There’s no Java collection in the standard library to do this. LinkedHashSet<E> preserves ordering similarly to a List, though, so if you wrap your set in a List when you want to use it as a List you’ll get the semantics you want. Alternatively, the Commons Collections (or commons-collections4, for the generic version) has a … Read more
Basically, it allows you to do this: callAPIThatTakesAMap(Collections.singletonMap(key, value)); rather than this: Map<KeyType, ValueType> m = new HashMap<KeyType, ValueType>(); m.put(key, value); callAPIThatTakesAMap(m); which is much nicer when you only have a single key/value pair. This situation probably does not arise very often, but singleton() and singletonList() can quite frequently be useful.
Use this method and pass your array in parameter Collections.shuffle(arrayList); This method return void so it will not give you a new list but as we know that array is passed as a reference type in Java so it will shuffle your array and save shuffled values in it. That’s why you don’t need any … Read more
If you look at the C# source code for List<T>, I think List<T>.AddRange() has optimizations that a simple loop doesn’t address. So, an extension method should simply check to see if the IList<T> is a List<T>, and if so use its native AddRange(). Poking around the source code, you see the .NET folks do similar … Read more
In short, the generic list does not have virtual methods for Add, Remove etc, as it was designed to be fast, not extensible. This means that you cannot swap this concrete implementation out for a useful subclass (even though you can subclass it as it is not sealed). Therefore, by exposing the List itself, you … Read more
The problem is that the way that List<T> detects modifications is by keeping a version field, of type int, incrementing it on each modification. Therefore, if you’ve made exactly some multiple of 232 modifications to the list between iterations, it will render those modifications invisible as far as detection is concerned. (It will overflow from … Read more
The behaviour is (somewhat) documented in the javadoc: This implementation determines which is the smaller of this set and the specified collection, by invoking the size method on each. If this set has fewer elements, then the implementation iterates over this set, checking each element returned by the iterator in turn to see if it … Read more