JAVA CONSTRUCTOR
- A class contains constructors that are invoked to create objects from the class blueprint.
- A constructor is a special method that is used to initialize a newly created object and is called just after the memory is allocated for the object.
- It can be used to initialize the objects ,to required ,or default valuesat the time of object creation It is not mandatory for the coder to write a constructor for the class
If no user defined
constructor is provided for a class, compiler initializes member variables to
its default values.
- numeric data types are set to 0
- char data types values are null
- Constructors are used to assign initial values to instance variables of the class.
- A default constructor with no arguments will be called automatically by the Java Virtual Machine (JVM).
- Constructor is always called by new operator. Constructors are declared just like as we declare methods, except that the constructor don't have any return type.
In order to create a Constructor observe the following rules
-
It has the same
name as the class
-
It should not return a
value not even void
-
You don't have to
provide any constructors for your class, but you must be careful when doing
this.
-
The compiler
automatically provides a no-argument, default constructor for any class without
constructors.
-
This default
constructor will call the no-argument constructor of the superclass. In this
situation, the compiler will complain if the superclass doesn't have a
no-argument constructor so you must verify that it does.
-
If your class has
no explicit superclass, then it has an implicit superclass of
Object, which does have a no-argument constructor.
Example:
class Sample_constructor
{
public static void main(String
args[])
{
Sample_constructor sam=new
Sample_constructor();
//object
is reated &
//constructor
is invoked using new
System.out.Println("Hai
...")
}
}
OUTPUT:
Hai...
NOTE:
· Though there is no constructor definition, Java defaultly
does the contructor process when method is invoked using new operator with tha
same name of class.
· Here there in this example there is no construction
defitions.but when code new Sample_contructor() is reached it creates &
initializes object
