Re: Does the clone() method of ArrayList<> make a copy of the objects in the ArrayList?

From:

Knute Johnson <nospam@rabbitbrush.frazmtn.com>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 03 Aug 2007 17:28:01 -0700

Message-ID:

<mKPsi.173957$wG2.128360@newsfe17.lga>

Arne Vajh?j wrote:

xz wrote:

anotherArrayList = (ArrayList<Something>) oneArrayList.clone();
anotherArrayList.get(0).makeSomeChange();

Will the change made in the second line make effect on
oneArrayList.get(0)?

clone is a shallow clone not a deep clone so yes.

Arne

Arne:

I know that it says in the docs that ArrayList.clone() is a shallow copy
and that the elements themselves are not copied. Why then does the
following code produce the following results (or have I gone completely
around the bend today?).

import java.util.*;

public class test9 {
     public static void main(String[] args) {
         ArrayList<Integer> list1 = new ArrayList<Integer>();
         list1.add(10);
         list1.add(11);
         list1.add(12);
         ArrayList list2 = (ArrayList)list1.clone();
         list1.set(0,20);
         list1.add(30);
         for (int i=0; i<list1.size(); i++)
             System.out.print(list1.get(i)+" ");
         System.out.println();
         for (int i=0; i<list2.size(); i++)
             System.out.print(list2.get(i)+" ");
     }
}

C:\Documents and Settings\Knute Johnson>java test9
20 11 12 30
10 11 12

--

Knute Johnson
email s/nospam/knute/