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:

class mp {
 Mp() {}
}

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:

class mp {
 mp() {
  System.out.println(“znl”);
 }
}

2. Parameterized Constructor

 

It is a type of constructor that requires the passing of parameters on the creation of the object.

 

For example: 

class mp {
 mp(int x) {
  System.out.println(“xml”);
 }
}

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.

class mp {
 mp() {
  System.out.println("yahoo");
 }
 mp(int a) {
  System.out.println("you have just selected constructor with integer value: " + a);
 }
 mp(float a) {
  System.out.println("you have just selected constructor with float value: " + a);
 }
 mp(int a, int b) {
  System.out.println("you have just selected constructor with integer values: " + a + " and " + b);
 }
 mp(int a, float b) {
  System.out.println("you have just selected constructor with integer value: " + a + " and float value: " + b);
 }
}
class sp {
 public static void main(String[] ab) {
  mp a1 = new mp();
  new mp(3);
  new mp(3, 2);
  new mp(3.3 f);
  new mp(4, 8.9 f);
 }
}

Output