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How do we copy objects in java?
In Java you can copy an object in several ways, among them, copy constructor and the clone method are the mostly used.
Using copy constructor
Generally, the copy constructor is a constructor which creates an object by initializing it with an object of the same class, which has been created previously. Java does support for copy constructors but you need to define them yourself.
Example
In the following Java example, we a have a class with two instance variables name and age and a parameterized constructor initializing these variables.
Then, we have another constructor which accepts an object of the current class and initializes the instance variables with the variables of this object.
If you instantiate this class using the second constructor by passing an object to it, this results an object which is the copy of the one which you passed as an argument.
import java.util.Scanner;
public class Student {
private String name;
private int age;
public Student(String name, int age){
this.name = name;
this.age = age;
}
public Student(Student 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();
Student std = new Student(name, age);
System.out.println("Contents of the original object");
std.displayData();
System.out.println("Contents of the copied object");
Student copyOfStd = new Student(std);
copyOfStd.displayData();
}
}Output
Enter your name Krishna Enter your age 20 Contents of the original object Name : Krishna Age : 20 Contents of the copied object Name : Krishna Age : 20
Using the clone method
The clone() method of the class java.lang.Object accepts an object as a parameter, creates and returns a copy of it.
Example
In the following Java example, we a have a class with two instance variables name and age and a parameterized constructor initializing these variables.
From the main method we are creating an object of this class and generating a copy of it using the clone() method.
import java.util.Scanner;
public class CloneExample implements Cloneable {
private String name;
private int age;
public CloneExample(String name, int age){
this.name = name;
this.age = age;
}
public void displayData(){
System.out.println("Name : "+this.name);
System.out.println("Age : "+this.age);
}
public static void main(String[] args) throws CloneNotSupportedException {
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();
CloneExample std = new CloneExample(name, age);
System.out.println("Contents of the original object");
std.displayData();
System.out.println("Contents of the copied object");
CloneExample copiedStd = (CloneExample) std.clone();
copiedStd.displayData();
}
}Output
Enter your name Krishna Enter your age 20 Contents of the original object Name : Krishna Age : 20 Contents of the copied object Name : Krishna Age : 20
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