Why do we need constructor?

Answer 1

when the object is instantiated(created) and delared,it has to assigned with variables.constructor is used for this purpose. syntax: classname ojbectname=new classname(); here classname() is a constructor. eg: box bb=new box(5,10); when this object is instantiated,it can be directly accessed by the constructor(similar to method but without a void because the instance variables are directly used) box(5,10) { }

Answer 2

The constructor is used to initialize each instance of the class, and place in in a proper state for further use. In particular, if the class contains pointers or references to other objects, the constructor allocates those objects and initializes the pointers or references. Of critical importance is the copy constructor, in a class with pointers. Without it, you get a shallow copy and run the risk of two pointers to the same object, and that is dangerous. With it, you can build and initialize smart pointers, or make deep copies, eliminating that problem.

Answer 3

To ensure that an object for the class can be created even though the programmer did not explicitly create one.

However, if you create a constructor with arguments, the system will not create the default constructor for your class

Answer 4

dynamically u can send the params by the time of object creation.

Classname obj = new Classname();

here Classname() is the constructor.

eg:

Box b= new Box(3,4);