Implementation Of Constructor in Java

What is constructor?

 
A constructor is a special type of method, of a class, that initializes the object of that type. It is an instance method that usually has the same name as the class.
   
Important points about constructors:
  1. It has no return type.
  2. It is called through the new keyword.
  3. A constructor has the same name as the class.
  4. Generally public or default.
For example:
  1. class mp {  
  2.  Mp() {}  
  3. }   

Types of constructor

 
There are two types of constructor as given below:
  1. Default constructor
  2. Parameterized constructor

1. Default Constructor

 
A "default constructor" refers to a null constructor that is automatically generated by the compiler, if no constructors have been defined for the class.
  
A programmer-defined constructor that takes no parameters, is also called a default constructor.
 
For example:
  1. class mp {  
  2.  mp() {  
  3.   System.out.println(“znl”);  
  4.  }  
  5. }   

2. Parameterized Constructor

 
It is a type of constructor that requires the passing of parameters on the creation of the object.
 
For example: 
  1. class mp {  
  2.  mp(int x) {  
  3.   System.out.println(“xml”);  
  4.  }  
  5. }  

Constructor Overloading

 
In Java, a constructor can be overloaded as a feature, of object-oriented programming.
 
Whenever multiple constructors are needed, they are implemented as overloaded methods. It allows more than one constructor inside the class, with a different signature.
  1. class mp {  
  2.  mp() {  
  3.   System.out.println("yahoo");  
  4.  }  
  5.  mp(int a) {  
  6.   System.out.println("you have just selected constructor with integer value: " + a);  
  7.  }  
  8.  mp(float a) {  
  9.   System.out.println("you have just selected constructor with float value: " + a);  
  10.  }  
  11.  mp(int a, int b) {  
  12.   System.out.println("you have just selected constructor with integer values: " + a + " and " + b);  
  13.  }  
  14.  mp(int a, float b) {  
  15.   System.out.println("you have just selected constructor with integer value: " + a + " and float value: " + b);  
  16.  }  
  17. }  
  18. class sp {  
  19.  public static void main(String[] ab) {  
  20.   mp a1 = new mp();  
  21.   new mp(3);  
  22.   new mp(32);  
  23.   new mp(3.3 f);  
  24.   new mp(48.9 f);  
  25.  }  
  26. }  

Output

 
Output