Sorry Posted before completing the message...

I was expecting an output of
Test1
Test2
Test3
Test4
Test1
Test2
Test3
Test4

But the Actual Output that I got was
Test1
Test2
Test3
Test4
Test1
Test2
Test5
Test6

I am confused with the behaviour on how the new values which has a
scope within the for loop be displayed outside without making any
changes to the main arraylist.

dshankh...@gmail.com wrote:

On Aug 23, 5:21 am, dshankh...@gmail.com wrote:

A note on style:

You should learn about and use Generics when dealing with collections.

List<List<String>> main = new ArrayList<List<String>>();
List<String> copy = new ArrayList<String>();

That way you no longer need to cast to ArrayList

main is almost a reserved word in Java.  It is used for the static
method that starts off an app. Using it for some other purpose is bit
like naming your son Susan and your daughter William and being puzzled
when others get confused.

I have converted your snippet to an SSCCE.
see http://mindprod.com/jgloss/sscce.html
I have also added some generics to make it clearer
what you are doing.
I have renamed your temp variables to make it clear
they are distinct.
I have added some labelling of the output.

You did not ask a question. Presumably you were expecting different
output than what you got. To me there were no surprises. Perhaps my
comments will explain what was troubling you.

import java.util.ArrayList;
import static java.lang.System.out;

public class CopyConfusion
  {
  /**
   * main startup method
   * @param args not used
   */
  public static void main ( String [] args )
     {
     ArrayList<ArrayList<String>> original = new
ArrayList<ArrayList<String>>();
     ArrayList<String> copy = new ArrayList<String>();
     copy.add("Test1");
     copy.add("Test2");
     original.add(copy);
     copy = new ArrayList<String>();
     copy.add("Test3");
     copy.add("Test4");
     // this adds the entire ArrayList as a single element, not the
individual Strings.
     original.add(copy);

     // original contains two ArrayLists at this point, each with two
Strings.
     out.println(">>>temp1");
     for ( int i=0;i<original.size();i++ )
        {
        final ArrayList<String> temp1 = original.get(i);
        for ( int j=0;j<temp1.size();j++ )
           {
           out.println(temp1.get(j));
           }
        }
     // output is
     // >>>temp1
     // Test1
     // Test2
     // Test3
     // Test4

     // The following code modifies the ArrayLists in the original.
     // Perhaps you were expecting get to hand you a clone rather
     // than the actual element.
     // Note that the for loop starts at 1 rather than 0.
     // This means you will leave original[0] intact.
     for ( int i=1;i<original.size();i++ )
        {
        final ArrayList<String> temp2 = original.get(i);
        temp2.set(0,"Test5");
        temp2.set(1,"Test6");
        }

     out.println(">>>temp3");
     for ( int i=0;i<original.size();i++ )
        {
        final ArrayList<String> temp3 = original.get(i);
        for ( int j=0;j<temp3.size();j++ )
           {
           out.println(temp3.get(j));
           }
        }
     // output is
     // >>>temp3
     // Test1
     // Test2
     // Test5
     // Test6

     }
  }