Java Constructor Examples

Example : A java program to show no argument constructor concept.

import java.io.*;
class Construct 
{
   int x;	  
   Construct() 
   {
      x = 10;  
   }
   public static void main(String[] args) 
   {
      Construct obj = new Construct();		
      System.out.println(obj.x); 		
   }
}

Output :
10

---------  OR  ----------

import java.io.*;
class Construct 
{
   int x;	  
   Construct() 
   {
      x = 10;
      System.out.println(x); 
   }
   public static void main(String[] args) 
   {
      new Construct();      	
   }
}

Output :
10

---------  OR  ----------

class Example 
{
   String nm;  
   Example()
   {
      nm= "Codershelpline";
      //this.nm="Codershelpline";
   }
   public static void main(String[] args) 
   {
      Example obj = new Example();
      System.out.println(obj.nm);
   }
}

Example : A Java program to show default as well as parameterized constructors.

import java.io.*;
class Construct 
{
   int x;	  
   Construct()      //Default Constructor
   {
       
   }
   
   Construct(int p)     //Parameterized Constructor
   {
       System.out.println(p);
   }
   
   public static void main(String[] args) 
   {
	new Construct();          // for default constructor only	
	Construct obj = new Construct(10);     //   for both default & parameterized constructor	
   }
}

Example : A Java program to show parameterized constructor.

import java.io.*;
  class Construct 
	{
	  int x;	  
	  Construct(int y) 
	  {
		x = y;  
	  }
	  public static void main(String[] args) 
	  {
		Construct obj = new Construct(25);		
		System.out.println(obj.x);		
	  }
	}

Output :
25

 ----------  OR  ------------

import java.io.*;
class Construct 
{
  int x;
  String str;  
  Construct(int y, String p) 
  {
   x = y;
   str=p;		
  }
  public static void main(String[] args) 
  {
	Construct obj = new Construct(25,"India");	
	System.out.println(obj.x+obj.str);	
  }
}
Output :
25India

 ----------  OR  ------------

import java.io.*;
class Construct 
{
  int x;
  String str;  
  Construct(int y, String p) 
  {
   x = y;
   str=p;		
  }
  void display()
  {
	System.out.println(x+"  "+str);  
  }
  public static void main(String[] args) 
  {
	Construct obj = new Construct(25,"India");	
	obj.display();
  }
}

Output :
25 India

Example : A java program to show constructor overloading.

class Example
{
      int x;
      //default constructor
      public Example()
      {
             x = 120;
      }
      //parameterized constructor
      public Example(int val)
      {
             x = val;
      }
      public int display()
      {
              return x;
      }
      public static void main(String args[])
      {
              Example obj1 = new Example();
              Example obj2 = new Example(50);
			  
              System.out.println(obj1.display());
              System.out.println(obj2.display());
      }
}

Output :
120
50

Example : A java program to show copy constructor.

class Example
{  
   String name;
   
   Example(String Str)
   {  
	name = Str;
   } 
   
   Example(Example obj3)
   {  
	this.name = obj3.name; 
        //name = obj3.name;
   }  
   void display()
   {
	System.out.println(name);
   }  

   public static void main(String args[])
   {  
	Example obj1 = new Example("Codershelpline");  
		
	obj1.display();
	Example obj2 = new Example(obj1);  
	  
	obj2.display();  
   }  
}

Output :
Codershelpline
Codershelpline