I am using a ConcurrentSkipListSet, that is obviously accessed through multiple threads. Now, the values that are used by the compareTo-method of the underlying objects change overtime. Because of this, I want to ‘update’ the ordering of the list (by resorting it, or something similar).
However, java.util.Collections.sort(list) doesn’t work, and just rebuilding the list is probably too slow (and would mess up the whole concurrency-proofness). Is there any other solution I should look at?
It does not have to lead to an optimal sort (which is near-impossible with concurrency and changing values anyway). Near optimal would suffice, as long as any remove/add-calls remain thread-proof (this would be a real issue when rebuilding the list when sorting).
Every time you edit an item such that it’s sort order may potentially change, you have to remove it from the list then change the key and then re-insert it.
Dr Cliff Click at Azul Systems has a very nice presentation of how they do lock-free hash-tables using tombstones and such. If you go towards writing your own skip-list/tree to make the reordering of an item into a single – and hopefully faster – op, then you might also go this lock-free route too. And be sure to share your results 🙂