JAVA CLASS CONSTRUCTOR

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

CONTRUCTOR DESCRIPTION:

• 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