Re: Handling the throwable "ThreadDeath"

Eric Sosman <>
Tue, 25 Aug 2009 18:27:51 -0400
Lew wrote:

Kidding aside, 'HashMap' is a close enough workalike to 'Hashtable'
absent multi-threaded concerns, as long as you take the extra step to
convert any associated 'Enumeration' into an 'Iterable' and replace any
lost methods ('contains()', etc.). If the 'Map' is shared, you would
want the 'Collections.synchronizedMap()' of it, or perhaps
'ConcurrentHashMap' (which covers 'Hashtable' functionality, too,
interestingly enough).

     Another difference between Hashtable and HashMap is their behavior
with null keys and values: HashMap is happy with them, while Hashtable
throws NullPointerException. It'd be a pretty weird program that
relied on getting NPE from a Hashtable to find out about nulls, but
we know that the set of weird programs is non-empty ...

     A more "practical" concern would likely be the different ways the
two implementations treat their chief tunables, load factor and initial
capacity. Somebody who's invested a lot of effort in choosing Just The
Right Size for his Hashtable, striking a delicate balance between lookup
time and iteration time, may be unhappy when HashMap inflates his
carefully-calculated size to the next power of two, potentially almost
doubling it.


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