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()   {  //constructor for class mp
   }
}

Types of constructor

There are basically 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 creation of the object.

For example:

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

Constructor Overloading

In Java, a constructor can also 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(3.3f);
        new mp(4,8.9f);
    }
}

Output