[collections] binary search removeAll/retainAll + other convenience methods

["matthew.hawthorne" <ma...@apache.org>]

Hi,

I have written a few methods in recent months that may fit with 
[collections].  I'll do a copy/paste of the signatures + javadoc 
descriptions.  Let me know what you think.

(Apologies if any of this functionality already exists in [collections]. 
  I took a quick look but didn't see any duplication.)


1) void removeAllUsingBinarySearch(List list1, List list2)

2) void retainAllUsingBinarySearch(List list1, List list2)

Functionally the same as List.removeAll(Collection) and 
List.retainAll(Collection), but uses a binary search in order to find 
the matches (as opposed to the linear search in Sun's default 
implementation).

(I was working with collections around 50,000 in size, and this made a 
very significant performance difference.)


3) List splitByMaximum(List items, int maxSize)

Splits a list into sublists.  Note that this method makes use of
java.util.List.subList(int fromIndex, int toIndex), so the result lists 
are backed by the original -- changes to the result lists affect the 
original list.

(I was in a situation where I had a large number of operations to 
perform, but due to memory constraints I had to limit the number of 
operations per transaction.  This did the trick.)


4) Map subMap(Map map, List keys)

Creates a subset of a map, containing only the specified keys.


5) List getMapValues(Map map, List keys)

Using the provided map, gets the values for the specified keys.


cheers,
matt


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