Object Cloning in Java

The object cloning is a way to create exact copy of an object. For this purpose, clone() method of Object class is used to clone an object.

The java.lang.Cloneable interface must be implemented by the class whose object clone we want to create. If we don't implement Cloneable interface, clone() method generates CloneNotSupportedException.

The clone() method is defined in the Object class. Syntax of the clone() method is as follows:

1. protected Object clone() throws CloneNotSupportedException  

Why use clone() method ?

The clone() method saves the extra processing task for creating the exact copy of an object. If we perform it by using the new keyword, it will take a lot of processing to be performed that is why we use object cloning.

Advantage of Object cloning

Less processing task.

Example of clone() method (Object cloning)

Let's see the simple example of object cloning

1. class Student18 implements Cloneable{  
2. int rollno;  
3. String name;  
4.   
5. Student18(int rollno,String name){  
6. this.rollno=rollno;  
7. this.name=name;  
8. }  
9.   
10. public Object clone()throws CloneNotSupportedException{  
11. return super.clone();  
12. }  
13.   
14. public static void main(String args[]){  
15. try{  
16. Student18 s1=new Student18(101,"amit");  
17.   
18. Student18 s2=(Student18)s1.clone();  
19.   
20. System.out.println(s1.rollno+" "+s1.name);  
21. System.out.println(s2.rollno+" "+s2.name);  
22.   
23. }catch(CloneNotSupportedException c){}  
24.   
25. }  
26. }  

Output:101 amit
       101 amit

As you can see in the above example, both reference variables have the same value. Thus, the clone() copies the values of an object to another. So we don't need to write explicit code to copy the value of an object to another.

If we create another object by new keyword and assign the values of another object to this one, it will require a lot of processing on this object. So to save the extra processing task we use clone() method.