From an email from Joe Bowbeer:

>TPE is the main consumer of ThreadFactory. There probably wouldn't be
>> a TF in j.u.c. if it weren't for TPE. (As I recall, TF didn't make
>> the first cut.)
>>
>> Currently the TF spec doesn't say what it does if it can't proceed.
>> Does it throw an exception or return null? Most people will assume it
>> does one or the other. But which?
>>
>> Unless null is mentioned in the doc, most people would not expect it,
>> because "null" is not the Java way. By explicitly handling null
>> return values, TPE is putting a stake in the ground. Without further
>> clarification, like #3 below, my interpretation of this is that TF
>> *can* return null.

...

>> Change ThreadFactory spec to reflect TPE reality: TFs can return null.

>> 1. Change ThreadFactory spec to reflect TPE reality:
>> TFs can return null.