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Re: A small quiz

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  Re: A small quiz Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-01 08:24 -0400
    Re: A small quiz e.d.programmer@gmail.com - 2015-10-01 08:33 -0700
      Re: A small quiz Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-01 11:41 -0400
        Re: A small quiz Eric Douglas <e.d.programmer@gmail.com> - 2015-10-01 08:59 -0700
          Re: A small quiz Jeff Higgins <jeff@invalid.invalid> - 2015-10-01 12:49 -0400
          Re: A small quiz Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-01 13:02 -0400
            Re: A small quiz Eric Douglas <e.d.programmer@gmail.com> - 2015-10-01 10:19 -0700
              Thanks (Was: A small quiz) j4n bur53 <janburse@fastmail.fm> - 2015-10-02 00:12 +0200
              Re: A small quiz Mike Amling <mamling@chaff.us> - 2015-10-02 09:18 -0500

#32746 — Re: A small quiz

On 10/1/2015 8:02 AM, Stefan Ram wrote:
>    A method m() is declared to have a return type of java.lang.String:
>
> java.lang.String m()
>
>    . A programmer writes this expression:
>
> java.lang.String.valueOf( m() )
>
>    (The scope is so that »m« in the above expression refers to the
>    method »m()« as declared above.)
>
>    . Can you find out what might be a good reason the programmer might
>    have to write this expression? Since the return type of m() already
>    /is/ java.lang.String, the call to »java.lang.String.valueOf« seems
>    to be completely superfluous!

     Please don't use the N-word, Stefan.

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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#32751

On Thursday, October 1, 2015 at 8:24:36 AM UTC-4, Eric Sosman wrote:
>      Please don't use the N-word, Stefan.

Which N-word, null?
Somehow I don't see the original message you're replying on.

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#32752

On 10/1/2015 11:33 AM, e.d.programmer@gmail.com wrote:
> On Thursday, October 1, 2015 at 8:24:36 AM UTC-4, Eric Sosman wrote:
>>       Please don't use the N-word, Stefan.
>
> Which N-word, null?

     Give the man a cigar!

> Somehow I don't see the original message you're replying on.

     Can't help you, I'm afraid.  Possibly something to do with
Stefan's fondness for the X-No-Archive header and similar
"implausible deniability" measures.

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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#32753

On Thursday, October 1, 2015 at 11:41:49 AM UTC-4, Eric Sosman wrote:
> > Which N-word, null?
> 
>      Give the man a cigar!
> 
> > Somehow I don't see the original message you're replying on.
> 
>      Can't help you, I'm afraid.  Possibly something to do with
> Stefan's fondness for the X-No-Archive header and similar
> "implausible deniability" measures.

That could explain it.  Did you see his message on a Google Group reader, or an email distribution list?

So the valueOf is pointless?
I tried this little test program:
public static void main(String[] args) {
     String s = null;
     System.out.println(s);
     System.out.println(String.valueOf(s));
     System.out.println(String.valueOf(null));
}
It didn't crash until it tried to get the valueOf the constant.

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#32754

On 10/01/2015 11:59 AM, Eric Douglas wrote:
>
> So the valueOf is pointless?
> I tried this little test program:
> public static void main(String[] args) {
>       String s = null;
>       System.out.println(s);
>       System.out.println(String.valueOf(s));
>       System.out.println(String.valueOf(null));
> }
> It didn't crash until it tried to get the valueOf the constant.
>
It would have, hadn't PrintStream checked for a null.

   public void print(String s) {
     if (s == null) {
       s = "null";
     }
     write(s);
   }

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#32755

On 10/1/2015 11:59 AM, Eric Douglas wrote:
> On Thursday, October 1, 2015 at 11:41:49 AM UTC-4, Eric Sosman wrote:
>>> Which N-word, null?
>>
>>       Give the man a cigar!
>>
>>> Somehow I don't see the original message you're replying on.
>>
>>       Can't help you, I'm afraid.  Possibly something to do with
>> Stefan's fondness for the X-No-Archive header and similar
>> "implausible deniability" measures.
>
> That could explain it.  Did you see his message on a Google Group reader, or an email distribution list?

     Neither: I used Thunderbird and news.eternal-september.org's
NNTP server.

> So the valueOf is pointless?
> I tried this little test program:
> public static void main(String[] args) {
>       String s = null;
>       System.out.println(s);
>       System.out.println(String.valueOf(s));
>       System.out.println(String.valueOf(null));
> }
> It didn't crash until it tried to get the valueOf the constant.

     A subtler quiz might be: Why does the final line crash when
the preceding line doesn't?  (And a further debate: Is the crash
a bug, or a feature, or a misfeature?)

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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#32756

On Thursday, October 1, 2015 at 1:02:17 PM UTC-4, Eric Sosman wrote:
>      A subtler quiz might be: Why does the final line crash when
> the preceding line doesn't?  (And a further debate: Is the crash
> a bug, or a feature, or a misfeature?)

Error is
Exception in thread "main" java.lang.NullPointerException
	at java.lang.String.<init>(Unknown Source)
	at java.lang.String.valueOf(Unknown Source)

Why does passing in a null constant generate this runtime error, and not a compile error?
It's just a confusing use of overload.
http://stackoverflow.com/questions/3131865/why-does-string-valueofnull-throw-a-nullpointerexception

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#32759 — Thanks (Was: A small quiz)

Eric Douglas schrieb:
> Why does passing in a null constant generate this runtime error, and not a compile error?
> It's just a confusing use of overload.
> http://stackoverflow.com/questions/3131865/why-does-string-valueofnull-throw-a-nullpointerexception

Was just wondering how long it takes me to find
the Java language choice rule for overloaded
Java class members. And here it is.

Currently doing an experiment in Prolog to Java
scripting, and need to code a dispatcher. An ad-hoc
dispatcher which uses the input order of the
Java class members already works:

Better Modules: An auto loader for overloaded members. (Jekejeke)
https://plus.google.com/+JekejekeCh/posts/SANxqdzvUaz

But I guess sooner or later I will need something
more intelligent and closer to the Java language
rules. Respecting the implements relation ship
of the base class to its super class is also on
the todo list.

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#32760

On 10/1/15 12:19 PM, Eric Douglas wrote:
> On Thursday, October 1, 2015 at 1:02:17 PM UTC-4, Eric Sosman wrote:
>>       A subtler quiz might be: Why does the final line crash when
>> the preceding line doesn't?  (And a further debate: Is the crash
>> a bug, or a feature, or a misfeature?)
>
> Error is
> Exception in thread "main" java.lang.NullPointerException
> 	at java.lang.String.<init>(Unknown Source)
> 	at java.lang.String.valueOf(Unknown Source)
>
> Why does passing in a null constant generate this runtime error, and not a compile error?
> It's just a confusing use of overload.
> http://stackoverflow.com/questions/3131865/why-does-string-valueofnull-throw-a-nullpointerexception

To preclude an unexpected choice of "Most Specific Method", I recommend 
always casting a null literal when used as a method argument.

System.out.println(String.valueOf((String)null)); // Prints "null".
System.out.println(String.valueOf((Object)null)); // Prints "null".
System.out.println(String.valueOf(null)); // NullPointerException

Mike Amling
RXZlbiB3aGVuIHRoZSBtZXRob2QgaXNuJ3Qgb3ZlcmxvYWRlZC4=

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