Deep copy in java example program

• Creating a copy of the object can be done in two ways 
• Shallow copy and deep copy. we have already discussed about shallow copy
• Shallow copy in java example program
• In shallow copy of object only object reference will be copied and if we change any data inside object changes will reflect in cloned object also this means both are referring to same object.
 

Deep copy / Deep cloning in  Java

• In deep copy completely a new object will be created with same data.
• If we change the data inside original object wont reflect in deeply cloned object.

Program #1: Java example program to demonstrate deep copy / deep cloning

Sample :

1. package com.shallowcopyvsdeppcopy;
2. 
   
3. public class Sample {
4. int a;
5. int b;
6. 
   
7. Sample (int a, int b){
8.     this.a=a;
9.     this.b=b;
10. }
11. 
    
12. }

Empclone :

1. package com.shallowcopyvsdeppcopy;
    
2. public class empclone implements Cloneable {
3.  
4.     Sample s;
5.     int a;
6.     
7.     empclone(int a, Sample s){
8.         this.a=a;
9.         this.s=s;
10.        
11.     }
12.      
13. public Object clone()throws CloneNotSupportedException{ 
14.        return new empclone(this.a, new Sample(this.s.a,this.s.a));
15. }  
16.            
17.     
18. public static void main(String[] args) {
19.      
20.         empclone a= new empclone(2, new Sample(3,3));
21.         empclone b=null;
22.     
23.  try {
24.              b=(empclone)a.clone();
25.            
26.  } catch (CloneNotSupportedException e) {
27.             // TODO Auto-generated catch block
28.             e.printStackTrace();
29.         }
30.         System.out.println(a.s.a);
31.         System.out.println(b.s.a);
32.        
33.         a.s.a=12;
34.         System.out.println(a.s.a);
35.         System.out.println(b.s.a);
36. }
37.  
38. }

OutPut:

1. 3
2. 3
3. 12
4. 3

What is the difference between shallow copy and deep copy:

• When we create a shallow copy of the object only reference will be copied
• When we create deep copy of the object totally new object with same data will be created. 
• Shallow copy and deep copy will be done by using Cloneable  interface in java.