I am wondering why the Framework doesn’t contain structures as Tree and Graph which are basic collections. Both can be regarded as sub types of Collection. This is a good question. I think it simply boils down to scoping. The core features that Collections API provides classes for are: iteration order: Lists and sorted maps … Read more
ListMap implements an immutable map using a list-based data structure, and thus preserves insertion order. scala> import collection.immutable.ListMap import collection.immutable.ListMap scala> ListMap(1 -> 2) + (3 -> 4) res31: scala.collection.immutable.ListMap[Int,Int] = Map(1 -> 2, 3 -> 4) scala> res31 + (6 -> 9) res32: scala.collection.immutable.ListMap[Int,Int] = Map(1 -> 2, 3 -> 4, 6 -> 9) … Read more
Your observation is spot on – in fact, it mirrors one made by Mads Torgersen, a Microsoft C# Language PM. Mads made a post in October 2006 on this subject titled What Is a Collection? in which he wrote: Admitted, we blew it in the first version of the framework with System.Collections.ICollection, which is next … Read more
Map.Entry is a key and its value combined into one class. This allows you to iterate over Map.entrySet() instead of having to iterate over Map.keySet(), then getting the value for each key. A better way to write what you have is: for (Map.Entry<String, JButton> entry : listbouton.entrySet()) { String key = entry.getKey(); JButton value = … Read more
As other people have mentioned, ArrayList has a constructor that takes a collection of items, and adds all of them. Here’s the documentation: http://java.sun.com/javase/6/docs/api/java/util/ArrayList.html#ArrayList%28java.util.Collection%29 So you need to do: ArrayList<MyNode> myNodeList = new ArrayList<MyNode>(this.getVertices()); However, in another comment you said that was giving you a compiler error. It looks like your class MyGraph is a … Read more
Yes, use the HttpRequest.QueryString collection: Gets the collection of HTTP query string variables. You can use it like this: foreach (String key in Request.QueryString.AllKeys) { Response.Write(“Key: ” + key + ” Value: ” + Request.QueryString[key]); }
All of these interfaces inherit from IEnumerable, which you should make sure you understand. That interface basically lets you use the class in a foreach statement (in C#). ICollection is the most basic of the interfaces you listed. It’s an enumerable interface that supports a Count and that’s about it. IList is everything that ICollection … Read more
Writing custom comparator in Java-8 is very simple. Use: Comparator.comparing(c -> c.lastUpdated); So if you have a List<Contact> contacts, you can use Contact lastContact = Collections.max(contacts, Comparator.comparing(c -> c.lastUpdated)); Or, using method references: Contact lastContact = Collections.max(contacts, Comparator.comparing(Contact::getLastUpdated));
Consider the following example: You have a simple data structure Data with a single property of type List. class Data(val items : List<String>) val dataObjects = listOf( Data(listOf(“a”, “b”, “c”)), Data(listOf(“1”, “2”, “3”)) ) flatMap vs. map With flatMap, you can “flatten” multiple Data::items into one collection as shown with the items variable. val items: … Read more
No, the immutability is only applied to the amount and references of the objects in the Collection, and does not address the mutability of objects you put in the Collection. What Immutable list gains over the standard JDK Collections.unmodifiableList is that by using ImmutableList you are guaranteed that the objects referenced, their order and the … Read more