![]() ![]() X: List = List(1, 2, 3, 4, 5, 6, 7, 8, 9)Īs you can see, this example creates a List of Int values, beginning at 1, and ending at 9. ![]() Create a Scala List with the ‘range’ methodĪnother convenient way to create a List is with the range method: In this example I've explicitly stated that the values in the List are of the Number type. This example demonstrates the syntax to specify the List type: Note that if you're going to mix types in a List constructor, you may need to manually specify the type of the List. This syntax looks a lot like the Java way to create an object, except (a) you don't need the "new" keyword before the List, and (b) you don't have to declare the type of elements in the List. My guess is that the most popular way to create a List is with what I call the "Java style": But I first learned about the :: approach many years ago with Lisp. (And yes, :: is a function/method.)Īrguably using this style can also be thought of as a Haskell or functional programming (FP) style. In this “cons” style, the :: method takes two arguments, a “head,” which is a single element, and a “tail,” which is a List. With this approach, you need to end the list with the Nil object. Create a Scala List in the Lisp styleįirst, if you prefer the Lisp-style of programming, you can create a Scala List using the “cons” syntax, like this:Īs you can see, this creates a List that contains the integers 1, 2, and 3. I'll execute each command in the Scala command-line interpreter so you can see the results of each approach. In this Scala List tutorial, I'll demonstrate each of these approaches. You can create a Scala List in several different ways, including these approaches: ![]() Scala List class FAQ: How do I create a List in Scala? show more info on classes/objects in repl.That's why if there are no constructors, java compiler will add a default constructor and calls super class constructor. But when you are inheriting some class it is your class responsibility to call super class constructor to make sure that super class initializes all its instance variables properly. Note: In side default constructor, it will add super() call also, to call super class constructor.Ĭonstructor's duty is to initialize instance variables, if there are no instance variables you could choose to remove constructor from your class. If there are no constructors added by you, then compiler generated default constructor will look like this. In your case, there is no default constructor as you are adding them programmatically. If a class doesn't have any constructor provided by programmer, then java compiler will add a default constructor with out parameters which will call super class constructor internally with super() call. the constructor has exactly the same effect whether they are included or not.the question got the defaults wrong, and.However, I am leaving it the answer because Technically it is not the constructor (default or otherwise) that default-initialises the fields. If a class contains no constructor declarations, then a default constructor with no formal parameters and no throws clause is implicitly declared. However, if you define at least one constructor, the default constructor is not generated. This is exactly the same as public Module()Īnd exactly the same as having no constructors at all. For your example, it would look like this assuming that the types are String, int and int, and that the class itself is public: public Module() Any uninitialised fields will be set to their default values. ![]() The default constructor is the no-argument constructor automatically generated unless you define another constructor. ![]()
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