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Java program to implement a copy constructor

Learn how to implement a copy constructor in Java?
Submitted by Nidhi, on March 21, 2022

Problem statement

In this program, we will create a Sample class with a parameterized and a copy constructor. A copy constructor is used to create an object using another object of the same class.

Source Code

The source code to implement a copy constructor is given below. The given program is compiled and executed successfully.

// Java program to implement a 
// copy constructor

class Sample {
  int num1;
  int num2;

  Sample(int n1, int n2) {
    this.num1 = n1;
    this.num2 = n2;
  }

  Sample(Sample obj) {
    this.num1 = obj.num1;
    this.num2 = obj.num2;
  }

  void printValues() {
    System.out.println("Data members: ");
    System.out.println("Num1: " + num1);
    System.out.println("Num2: " + num2 + "\n");
  }
}

class Main {
  public static void main(String args[]) {
    Sample obj1 = new Sample(10, 20);
    Sample obj2 = new Sample(obj1);

    obj1.printValues();
    obj2.printValues();
  }
}

Output

Data members: 
Num1: 10
Num2: 20

Data members: 
Num1: 10
Num2: 20

Explanation

In the above program, we created a Sample class and public class Main. The Sample class contains data members num1, num2, and a parameterized constructor, a copy constructor, a method printValues().

The Main class contains a static method main(). The main() is an entry point for the program. Here, we created 2 objects obj1, obj2. We initialized data members of obj1 using parameterized constructor and initialized object obj2 using the copy constructor. After that, we printed the result.

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