Re: Overflowing HashMap

David Lamb wrote:


Maps don't have indices.

But whether they're limited to 'int' range capacity is very easy to check.

Sure enough, right there in the source for 'HashMap', is

     transient Entry[] table;

But all of that is unnecessary effort. I can't believe I bothered, lazy as I
am, given that the Javadocs guarantee that a 'Map' can hold at most
'Integer.MAX_VALUE' elements usefully. (In principle there's no reason a
'TreeMap' couldn't hold more than that, but it would likely become unuseful at
that point. For example, 'putAll(sortedMapOverSized)' might surprise you.)

<http://docs.oracle.com/javase/7/docs/api/java/util/Map.html#size()>
<http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/7-b147/java/util/HashMap.java>
<http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/7-b147/java/util/TreeMap.java>

P.S., 'TreeMap' has an interesting expression to handle the infamous overflow
bug for tree sorting/searching of which Josh Bloch has red-facedly written:

   int mid = (lo + hi) >>> 1;

P.P.S, Yes, I know that source comes from a pretty old Java version (b147),
but that shouldn't matter here. That site didn't have newer and it's too well
organized to ignore.

--
Lew
Honi soit qui mal y pense.
http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg