Re: How to check variables for uniqueness ?
Lew wrote:
Ed wrote:
And in case anyone's interested, here are the times for HashMap. Looks
like Map is in the league of Set, and not the slow-moving List. (These
times are longer than the previous times because of current CPU
loading; relativity is the key.)
522393 duplicated words. Using java.util.HashSet, time = 789ms.
522393 duplicated words. Using java.util.TreeSet, time = 2168ms.
522393 duplicated words. Using Map , time = 1180ms.
522393 duplicated words. Using java.util.ArrayList, time = 183795ms.
522393 duplicated words. Using java.util.LinkedList, time = 274781ms.
These times are extremely interesting.
I speculate that the greater part of the difference between HashMap and
HashSet would be the second loop through the Map. Note that though the
Map was slightly slower than the Set, it delivers more information. With
the Set you only knew how many words were duplicated; with the Map you
can also figure out which words were, and how many times each one occurred.
You could, for example, use the Map to deliver the words in order of
frequency, given the right comparator over the entry set.
A lot of the Map slowness is probably the churn of Integer objects
created. Using an int[1] as a "mutable Integer" would work far better
(although mutable objects in collections is normally bad, mutable values
in a map isn't generally a problem, so long as you don't have mutable keys).
On the subject of tabs, my copy of Thunderbird seems to be quietly
converting tabs into spaces, though I can't find the setting for it.
Posts apparently originally containing tabs (e.g. Ed's earlier) have
spaces when I view them, and my own posts written with tabs don't make
you complain. :) The curious thing is that incoming posts seem to have
tab->4 spaces and the editor shows tabs as 8 spaces, but they become 4
in the actual sent posting...and none of the options in Thunderbird say
anything about conversion of tabs at all, either to set their displayed
width or to actually change tabs to certain numbers of spaces. Hrm. The
"online help" doesn't open a help window, but rather hijacks my open
Firefox window, and the search there is useless on this topic too...