What is a copy constructor in Java?

Question

Can anybody tell me what is copy constructor in Java?

Answer 1

In a copy constructor, an object is created by initializing it with an object of the same class, which has been created earlier.

Java does not provide an explicit copy constructor, the user needs to define itself.

Code:

import java.util.Scanner;

public class Employee {

   private String name;

   private int age;

   public Employee(String name, int age){

      this.name = name;

      this.age = age;

   }

   public Employee(Employee std){

      this.name = std.name;

      this.age = std.age;

   }

   public void displayData(){

      System.out.println("Name : "+this.name);

      System.out.println("Age : "+this.age);

   }

   public static void main(String[] args) {

      Scanner sc =new Scanner(System.in);

      System.out.println("Enter your name ");

      String name = sc.next();

      System.out.println("Enter your age ");

      int age = sc.nextInt();

      Employee std = new Employee(name, age);

      System.out.println("Contents of the original object");

      std.displayData();

      System.out.println("Contents of the copied object");

      Employee copyOfStd = new Employee(std);

      copyOfStd.displayData();

   }

}

Here,  a copy constructor is created which accepts an object of the current class and initializes the values of instance variables with the values in the obtained object. If a user creates an object and invokes the copy constructor bypassing it, an earlier created copy of the object is given to the user.