Kotlin also lets us create an initialization block that runs immediately after our properties have been set. This primary constructor has two properties: name and roll. Here, (val name: String, var roll: Int), is the primary Constructor. We aren’t limited to just setting properties in a constructor. In Kotlin language, the Constructor is declared with the class header, unlike Java, where you have to declare the Constructor in the class body. This lets use print Bob’s position in the println statement. Since we used the val keyword in front of the position argument, Kotlin created a position property on Bob. When we create an instance of Bob, we have to supply a String to the constructor. Notice how the Bob class has a position parameter of type String. When you're annotating a property or a primary constructor parameter, there are multiple Java elements which are generated from the corresponding Kotlin element, and therefore multiple possible locations for the annotation in the generated Java bytecode. We can also define constructors that force us to use valid data. When we create a ChalkBoard object, we just use the () for the default constructor.
When no constructor is specified, Kotlin will supply an empty no argument constructor. Let’s walk through the various forms of constructors we can define in Kotlin. The other constructor takes an existing collection object and automatically adds all objects contained in the collection passed into the constructor into the new list. The first constructor is called the default constructor and accepts no arguments.
#Kotlin constructor code#
The above Java code snippet demonstrates multiple constructor. Let’s consider the constructor found in the ArrayList class found in .ĪrrayList list = new ArrayList() //Default constructorĪrrayList list2 = new ArrayList(list) //Secondary constructor Like all methods, constructors can have zero or more parameters. The primary constructor is part of the class header: it goes after. The constructor runs when an instance of a class is created. A class in Kotlin can have a primary constructor and one or more secondary constructors. Such code is referred to as a constructor method. Many OOP languages have special code that is used to initialize a class to a valid state.
0 kommentar(er)
