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What do you mean by Constructor?

Posted By :PLC Technologies     Posted Date :December 17, 2014    Points :40   Category :JavaScript/VBScript 
Constructor gets invoked when a new object is created. Every class has a constructor. If we do not explicitly write a constructor for a class the java compiler builds a default constructor for that class.

You can also find related Interview Question to What do you mean by Constructor?  below: 

Difference between type constructor and instance constructor? What is static constructor, when it will be fired? And what is its use?

  
(Class constructor method is also known as type constructor or type initializer)
Instance constructor is executed when a new instance of type is created and the class constructor is executed after the type is loaded and before any one of the type members is accessed. (It will get executed only 1st time, when we call any static methods/fields in the same class.) Class constructors are used for static field initialization. Only one class constructor per type is permitted, and it cannot use the vararg (variable argument) calling convention. (More...)

What is Private Constructor? and it's use? Can you create instance of a class which has Private Constructor?

  
When a class declares only private instance constructors, it is not possible for classes outside the program to derive from the class or to directly create instances of it. (Except Nested classes)
Make a constructor private if:

1) You want it to be available only to the class itself. For example, you might have a special constructor used only in the implementation of your class' Clone method.

2) You do not want instances of your component to be created. For example, you may have a class containing nothing but Shared utility functions, and no instance data. Creating instances of the class would waste memory. (More...)

Constructor and Destructor

  
Constructor

1. The Constructor is the first method that is run when an instance of a type is created. In visual basic a constructor is always Sub new ().

2. Constructor are use to initialize class and structure data before use. Constructor never returns a value and can be overridden to provide custom initialization functionality.

3. The constructor provides a way to set default values for data or perform other necessary functions before the object available for use.

Destructor:
-------------
Destructors are called just before an object is destroyed and can be used to run clean-up code. You can't control when a destructor is called. (More...)

What is a private constructor? Where will you use it?

  
When you declare a Constructor with Private access modifier then it is called Private Constructor. We can use the private constructor in singleton pattern.

If you declare a Constructor as private then it doesn't allow to create object for its derived class, i.e you loose inherent facility for that class. (More...)

What is Static Constructor?

  
It is invoked when the instance of the class is created. (More...)

What exactly a Constructor is doing ?

  
Constructor Creates as well as Initialized the objects. (More...)

What is the work of a constructor?

  
Constructor creates and initialises the objects in an application. (More...)

A constructor can be private. True or False

  
False. A constructor should not be private. (More...)

Static datamembers should be initialized inside the constructor. True or False.

  
False. Static datamembers should not be initialised inside constructor. (More...)

Whether we can create a private constructor for a class?

  
Yes it is possible. we can create a private constructor for a class (More...)

Where we can use the private constructor?

  
A private constructor is a special instance constructor. It is commonly used in classes that contain static members only. (More...)

Which design pattern should have private or protected constructor?

  
singleton design pattern should have private or protected constructor (More...)

What is Constructor and distructor?

  
Constructor is a Special Method Having Same Name as That of Class-which is Invoked whenever the instance of Class is Created.


Distructor is a Special Method Having Same Name as That Of Class Prefixed with Symbol Tilde(~)-which is Called After Removing the object From the memory.it is used to collect the Garbage from the memory. (More...)

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