Question

Using Java 1.6 and the AtomicLongArray, I’d like to “copy” the original AtomicLongArray into a new one. There is a constructor that takes an array (AtomicLongArray(long[])), so I thought I could just get the array from the original one and give it to the constructor.

Sadly, the actual long[] in the AtomicLongArray is private and there seem to be no getters for it. Is there any way to do this, meaning copy the values from one AtomicLongArray to another? I can’t create my own class based on this class, as the sun.misc.Unsafe class is not available to me.

This is needed because I’m going to iterate over the values, and I don’t want them modified by another thread during iteration. So I thought I could make a copy and use that for the iteration…

Thanks!
Phillip

Answer 1

I suspect you have to create your own long[] and populate it first, or just iterate over the original:

AtomicLongArray copy = new AtomicLongArray(original.length());
for (int i = 0; i < copy.length(); i++)
{
    copy.set(i, original.get(i));
}

Note that although each individual operation in AtomicLongArray is atomic, there are no bulk operations – so there’s no way of getting a “snapshot” of the whole array at time T. If you want that sort of behaviour, I believe you’ll need to use synchronization.