Constructor in java

 Constructor:

• A constructor is one kind of feature in oops.
• Constructor means, class name the same as the function or method name.
• It is similar to the function so it’s called a special member function and that class name the same as the constructor name.
• It used to construct and initialize all the data members.
• Constructor automatically called, when the object is created.
• It can be defined inside the class and definitions are outside the class definition help of the class name. 

Special characteristics of the constructor:

• A constructor should be declared in the public section.
• The name should be equal to the class name followed by the parenthesis.
• It does not have any return type, not even void.
• They cannot be inherited through a derived class can call the base class constructor.
• It cannot be a virtual function.

Types of the constructor:

• Three different types of constructors:

           1. Default constructor
           2. Parameterized constructor
Default constructor:

• A constructor with no parameters is known as a default constructor.

Syntax:

1. clclass class_name

   {

   class_name ()

   {

             //Statements

   }

   Main function()

   {

             //Object creation:

             Class_name object_name=new class_name();

             //Object calling:

             Object_name.method_name();//If constructor of method then no need this line.

   }

   }

Example:

1. import java.util.Scanner;

   public class Default_constructor {

   int a,b;

   Scanner sc = new Scanner(System.in);

   Default_constructor()//no parameter with constructor

   {

           System.out.println("Enter a and b value: ");

           a = sc.nextInt();

           b = sc.nextInt();

           System.out.println("Addition value is:" + (a + b));

       }

       public static void main(String args[]) {

           Default_constructor d = new Default_constructor();

       }

   }

Output:

Parameterized constructor:

• A constructor with parameters is known as a parameterized constructor.

Syntax:

1. clclass class_name

   {

   class_name (parameter_list)

   {

             //Statements

   }

   Main function()

   {

             //Object creation:

             Class_name object_name=new class_name(parameter_list);

             //Object calling:

             Object_name.method_name(parameter_list_of_values);

   }

   }

Example:

1. public class Parameterized_constructor {

       int roll_num, mark;

       String name;

       Parameterized_constructor(int x, String y, int z) {

           roll_num = x;

           name = y;

           mark = z;

           System.out.println("Roll Number\t Student Name\t Student total mark");

           System.out.println(roll_num + "\t\t " + name + "\t\t " + mark);

       }

    

       public static void main(String args[]) {

           Parameterized_constructor p1 = new Parameterized_constructor(01, "Ahamed", 455);

           Parameterized_constructor p2 = new Parameterized_constructor(02, "Bhanu", 337);

       }

   }

Output:

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