The Significance of Using Constructor In Java

Posted By : Jatin Singh | 31-Oct-2020

constructor in java




A constructor is a non-static member function of a class declared with the same name as the name of the class. It is a nor return type function and a constructor is used to initialize the objects of class.

Non-Static function:-In java if we define a function without using any keyword then by default it is a non-static function.


class Documentation {

   Documentation () {



 Explanation of above syntax:- A class is created with name "Documentation" and having a constructor "Documentation" with same name as class name and it is a non-static function.


Key Features:-

 1- When no constructor is defined in the program then the compiler provides the default constructor for the class.

2- Constructor can be parameterized.

3- Constructor can be overloaded which mean we can define more than one constructor in a class.



  1. Parameterized Constructor 
  2. Non-Parameterized Constructor

 Parameterized Constructor:-

    A constructor defined by passing arguments then is known as a parameterized constructor.


class Constructor {

   int a;

   Constructor(int a ) { //Parameterized constructor

      a = i;


public class Cons {

   public static void main(String args[]) {

      Constructor c1 = new Constructor();





Explanation of above code:-

  A class "Constructor" is created and having a parameterized constructor define with same name as the name of class "Constructor(int a)" where "int a" is a parameter so, it is called as parameterized constructor and in class "Cons" a constructor is called with the help of object "c1" of class "Constructor".



Non-Parameterized Constructor:-

    A constructor defined without passing argument is then known as a non-parameterized constructor.


 Class Rectangle{

  private int l,b,h;

  public Rectangle() { //Non-Parameterized Constructor






public class Construct {

   public static void main(String args[]) {

      Rectangle b1 = new Rectangle();


      System.out.println("Length of box : "+l);

      System.out.println("Breadth of box : "+b);

      System.out.println("Height of box : "+h);



Length of box : 10

Breadth of box : 10

Height of box : 10


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