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Deep Copy And Shallow Copy

Let us elaborate it with an example

Shallow Copy

I am declaring 2 arraylist

ArrayList a = new ArrayList(); 
ArrayList b = new ArrayList();

Now I have added an element in the arraylist

a.Add("2");

Now use the clone method

b = (ArrayList)a.Clone(); // shallow copy

Now if you see no of elements in b, it will show 1

and no of elements in a is also 1 i.e. "2"

Now add another element in an arraylist a

a.Add("3");

Now if you see no of elements in b, it will show 1

and no of elements in a is also 2 i.e. "2" and "3".

shallow copy allows you to replicate the arraylist once. it then ignores the relationship it has with the original array.

Deep Copy

Now consider the example above

instead of using clone method use

b = a;

Now if you see no of elements in b, it will show 1

and no of elements in a is also 1 i.e. "2"

Now add another element in an arraylist a

a.Add("3");

Now if you see no of elements in b, it will show 2

and no of elements in a is also 2 i.e. "2" and "3".

The deep copy will be persistent and any changes you make to the original arraylist will be reflected in both copies.

Posted By -	Karan Gupta

Posted On -	Wednesday, May 5, 2010

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