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Constructor in java

Constructor
  • Constructor is special member of class it is used to initialize data
    member of class at time of object creation.
  • Every class must have constructor either user define or
    compiler define(default constructor)
  • Constructor define by programmer is known user define constructor where as constructor define by compiler is known as default constructor.
  • If user not define constructor then compiler automatically define
Two types of Constructor
  1. User define
  2. Compiler define
  • Constructor without any parameter is known as zero parameter or no argument constructor
  • Constructor define with parameter is known as parametarized constructor.
  • parametarized constructor used to pass value in constructor.
  • Constructor name same as class name
  • Constructor has no return type
constructor overloading
  •  In a class we can define any number of constructor is know as overloaded
    constructor.
  •  Whenever we create overloaded constructor argument should be differ in
    terms argument type or argument length.
  •  The overloaded constructor are used to create object with different
    initialization
  • Constructor returns the object address which is constructed by constructor
    of class.
Example of Overload Constructor and parametarized constructor
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package constructor;
class Demo1
 {
	int a=10;
	int k;
	double d;
 
	//zero argument constructor
	Demo1()
	{  
		k=12;
		d=12.4;	
	}
	// u can overload the constructor
	// but argument should differ in terms of argument 
        //                                     type or length of argument
 
 
	Demo1(int a) //Parameterized constructor
	{
		this.a=a;
	}
 
 } 
 
public class Sample1
{
	public static void main(String[] args)
	{
		System.out.println("*************************");
 
		Demo1 obj1=new Demo1();
 
		System.out.println("k value : "+obj1.k);
 
		System.out.println("d value :"+obj1.d);
 
		Demo1 obj2=new Demo1(12);
 
        System.out.println("a value : "+obj2.a);
 
        System.out.println("*************************");
	}
 
}
 
output:
 
*************************
k value : 12
d value :12.4
a value : 12
*************************