AS3 / Flex性能-新的ArrayList与ArrayList.removeAll（）

Question

What is actually faster? Simply creating a new ArrayList/ArrayCollection or re-using an existing one and remove its elements?

I'm developing for mobiles where performance is always an issue, so I'm after the fastest method.

Answer 1

Here's an interesting blog post on optimization of clearing an ArrayList/ArrayCollection. Apparently, setting mycollection.source = new Array() is significantly faster than mycollection.removeAll() with large data sets, as removeAll ensures that all event listeners are removed.

As this is the case, most likely new ArrayList would beat ArrayList.removeAll(), but new source Array may be the better option, as it should have less of an impact on bindings/listeners.

Answer 2

even faster is mycollection.source = []; (as opposed to mycollection.source = new Array() )

Another option is to use linked lists and object pools. Object pools allow the objects to have their properties re-written instead of deleting an object and creating a new one. If you then keep them in a linked list instead of an array, looping through them is a lot faster. So if you just want to loop through a bunch of objects, go with linked lists, but if you need to do any sorting, then the array and vectors would be faster.

Another concern is memory use. not just for keeping applications running memory smaller, but the more objects you declare, the more work the garbage collector has to do when it comes time for clean-up.