Constructors in Java

  Constructors in Java 

It can be tedious and sometimes nightmares to initialize all variables in a class each time an instance is created. It would be simpler to have all the initialization done at the time of object creation itself. As the initialization is so common Java allows objects to initialize themselves whenever they are created. This automatic initialization of the object during creation is done by a special function called as constructor. 

So as the above syntax shows , the constructor is a specialized method of a class which has the same name as the class name and the constructor gets automatically gets invoked whenever an object of the class is created and is used to initialize the private data members.

Now, consider a small program which includes the creation of object "obj" of class Printing. 

In the above program, when the control encounters the new keyword memory for the new object is allocated and the  constructor immediately creates and  initializes the object of Printing Class. 

 In simple words, for the above program whenever the main() method is executed, object "obj" of type Printing is created. The moment the object is created the constructor gets executed and you get the output as "Hello World!"

                     Need For Constructors

 In general it is best that all the objects are initialized when they are ceated.
However sometime we cannot initialize the object as we initialize the primitive members.
Consider the simple program given below which try to initialize the fields of class Car just as same as initializing the primitive data types.

In the above programs we can see that java gives an error when we try to initialize "obj1" . So to initialize the members or fields for an Object we use Constructors.

The functioning of the constructor  and more programs involving constructors will be discussed in the next post.