Java List.SubList（）性能比较

Question

I need to implement a sliding window which slides over a sequence. (1:[0,1,2,3]2:[1,2,3,4],...) Which aprove might be faster? 1.

for each step i; {List=wholeList.sublist(i,i+windowlen)}

or 2.

  List window=wholeList.sublist(0,window);
  for each i{
  window.remove(0);
  window.add(i+windowlen);

}

?

I measured the time with system.currtime bla .. +-std the SubLists seems to work faster.. but why? i think the second aproach is O(n)

I need to operate huge databases.. therefor i need to look at this..

mfg Jan

Answer 1

Assuming the remove step is only part of step 2, they aren't equivalent, so comparing them is pointless. The second one modifies both the subsist and the underlying list. I doubt whether (2) will even work. I don't see any reason to go beyond (1).