Groups > comp.lang.java.programmer > #25977

Re: JLS 3/e -- Lots Of Errors

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From	Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand>
Newsgroups	comp.lang.java.programmer
Subject	Re: JLS 3/e -- Lots Of Errors
Followup-To	comp.lang.java.programmer
Date	Mon, 07 Feb 2011 12:31:07 +1300
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In message <SMw3p.72075$ZS4.20129@newsfe07.iad>, Arved Sandstrom wrote:

> On 11-02-06 12:18 AM, Lawrence D'Oliveiro wrote:
>
>> In message<40p3p.37003$5k5.12664@newsfe03.iad>, Arved Sandstrom wrote:
>>
>>> On 11-02-05 11:41 PM, Lawrence D'Oliveiro wrote:
>>>
>>>> In message<%8o3p.61505$8_2.1344@newsfe17.iad>, Arved Sandstrom wrote:
>>>>
>>>>> On 11-02-05 10:14 PM, Lawrence D'Oliveiro wrote:
>>>>>
>>>>>> In message<iijn9l$ccs$2@news.albasani.net>, Lew wrote:
>>>>>>
>>>>>>> Lawrence D'Oliveiro wrote:
>>>>>>>
>>>>>>>> * Section 4.5.1.1, page 55:
>>>>>>>>
>>>>>>>>          T<= ? extends T
>>>>>>>>          T<= ? super T
>>>>>>>>
>>>>>>>> One of these is the wrong way round.
>>>>>>>
>>>>>>> Nope.  Both are true.
>>>>>>
>>>>>> In that case, why is one called an “upper bound” and the other a
>>>>>> “lower bound”?
>>>>>
>>>>> Because the first (? extends T) specifies an upper bound (namely T),
>>>>> and the second (? super T) specifies a lower bound (in this case also
>>>>> T).
>>>>
>>>> So do you understand what the “<=” symbol is supposed to represent?
>>>>
>>> It represents precisely and exactly what this sentence:
>>>
>>> "A type argument TA1 is said to contain another type argument TA2,
>>> written TA2<= TA1, if the set of types denoted by TA2 is provably a
>>> subset of the set of types denoted by TA1"
>>
>> So look again at the two relations I quoted above, and see how the
>> definition you quoted is consistent with one of them, but not the other.
>> Hint: go and look up the meaning of “extends” if you have to.
> 
> I'm cool with "extends" in wildcards ...

Is a type that “extends” T a subclass or a superclass of T?

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Thread

Re: JLS 3/e -- Lots Of Errors Lew <noone@lewscanon.com> - 2011-02-05 09:36 -0500
  Re: JLS 3/e -- Lots Of Errors Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-02-06 21:29 -0500
    Re: JLS 3/e -- Lots Of Errors Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-02-06 22:00 -0500
      Re: JLS 3/e -- Lots Of Errors Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-02-08 09:20 +1300
    Re: JLS 3/e -- Lots Of Errors Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-02-07 15:45 +1300
  Re: JLS 3/e -- Lots Of Errors Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-02-06 08:48 -0400
    Re: JLS 3/e -- Lots Of Errors Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-02-07 12:31 +1300
      Re: JLS 3/e -- Lots Of Errors Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-02-06 20:44 -0500
        Re: JLS 3/e -- Lots Of Errors Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-02-07 14:50 +1300

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