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Object tracking ( again )

Posted on 2004-09-02
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Last Modified: 2010-03-31
Hi,
  A while ago when I was first getting in to Java I asked you guys the best way to track objects - which is the good old ArrayList. This worked perfectly as all I needed to do was read data from the objects and so I was happy and content. Today though, I need to write back to the objects in the array. I've got this so far :


Object test = (Object)arrayList.get(0);


My question is whether or not this creates another copy or whether it's a reference to the object that already exists. I think it's a reference as I'm not using "new" to instantiate a new one.... but I figured I'd ask because even if I test it, my test might be flawed, leading me to the wrong conclusion.... so once again I have to ask for your assistance :)

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Question by:petepalmer
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5 Comments
 
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by:
expertmb earned 65 total points
ID: 11962129
>>whether it's a reference to the object that already exists.
it's a reference to the object that already exists.
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by:TimYates
TimYates earned 30 total points
ID: 11962140
yup
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by:expertmb
expertmb earned 65 total points
ID: 11962151
>> I need to write back to the objects in the array.

you can do like this also
Object[] object = arrayList.toArray();
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Assisted Solution

by:zzynx
zzynx earned 30 total points
ID: 11962193
>> it's a reference to the object that already exists.
Indeed. So you can change it and the changes will take place in the list.

>>Object test = (Object)arrayList.get(0);
I guess you mean

       MyOwnObject test = (MyOwnObject)arrayList.get(0);

       test.myFunction();  // will adapt the entry in the list
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Expert Comment

by:zzynx
ID: 11962236
Thanks :)
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