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Thread: Deep copy of ArrayList?

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    Member Scotty's Avatar
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    Default Deep copy of ArrayList?

    Does:
    array.add(data.get(y));
    make a deep or shallow copy? I am trying to get an arrayList to collect data but iterating though an algorithm and then place that data into a new arrayList three times. Each new array has if (i = 0), if (i=1) etc around it, but they all have the same data at the end! (only Integer objects).

    I have been writing code for 2 days now, please feel free to point out the obvious.

    Thanks


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    Crazy Cat Lady KevinWorkman's Avatar
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    Default Re: Deep copy of ArrayList?

    Assuming that data and array are both ArrayLists, and y is some index, then the same Object will be in both ArrayLists. You can test this just by using the == operator on the references returned by the get() methods of each ArrayList.
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    Member Scotty's Avatar
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    Default Re: Deep copy of ArrayList?

    But is it a deep copy? As when I replace the data in the first arrayList (array) then both the arrayLists change. (That or I have another error)

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    Default Re: Deep copy of ArrayList?

    What happened when you tried? It shouldn't be too hard to throw together a test program that tests this out. I'm really not even sure what you're asking- you mean if you modify the Object that's in both ArrayLists? Or if you add a new Object to one of the ArrayLists?
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