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What is the use of Constructor
8 ответов
+ 26
Ytbarek Gebre
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A 'constructor' initializes an object when it is created. It has the same name as its class and is syntactically similar to a method.
However, constructors have no explicit return type. The general form of a constructor is:
access class-name(param-list) {
// constructor code
}
Typically, you will use a constructor to give initial values to the instance variables defined by the class or to perform any other startup procedures required to create a fully formed object.
Also, usually, access is 'public' because constructors are normally called from outside their class. The param-list can be empty, or it can specify one or more parameters.
All classes have constructors, whether you define one or not, because C# automatically provides a default constructor that causes all member variables to be initialized to their default values.
+ 17
creating objects of the defined class initiating data members and calling constructors of the parents if the class extends any other classes
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So when you create a class usually you will have⬇
public class Car{
//empty fields⬇
String model;
int year;}
The best way to initalize these fields is with the constructor.
public class Car{
String model;
int year;
//constructor method⬇
Car(String model, int year){
this.model= model;
this.year=year;}
}
Now when you create an instance of class a call to the constructor is made which initalize the fields for your new instance.
Car mini = new Car("mini",1997);
System.out.print(mini.year);
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Initalize an instance of an class (object) with an valid state.
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You can overload the constructor to use different number or type of parameters to instantiate object of the class. This leads to run-time polymorphism... 🤔
+ 2
You can use constructors to create objects with special methods.
You can define how the created object behaves for any operators.
You can make a program to print "Hello world!" When an object is divided by 5.
You can make a program to print "SoloLearn" when an object is compared.
0
The visibility is NOT usually public. In OOP you often use other qualifiers to hide the constructors that have technical relevance only.