Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.java.help > #1856 > unrolled thread

Brain teaser for newbies

Back to article view | Back to comp.lang.java.help

Contents

  Brain teaser for newbies Roedy Green <see_website@mindprod.com.invalid> - 2012-06-13 13:21 -0700
    Re: Brain teaser for newbies Lew <lewbloch@gmail.com> - 2012-06-13 14:15 -0700
      Re: Brain teaser for newbies Roedy Green <see_website@mindprod.com.invalid> - 2012-06-13 20:46 -0700
        Re: Brain teaser for newbies Lew <noone@lewscanon.com> - 2012-06-13 22:43 -0700
          Re: Brain teaser for newbies Roedy Green <see_website@mindprod.com.invalid> - 2012-06-14 11:06 -0700
            Re: Brain teaser for newbies markspace <-@.> - 2012-06-14 11:45 -0700
          Re: Brain teaser for newbies Roedy Green <see_website@mindprod.com.invalid> - 2012-06-14 11:14 -0700
            Re: Brain teaser for newbies Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-14 12:17 -0700
              Re: Brain teaser for newbies Roedy Green <see_website@mindprod.com.invalid> - 2012-06-14 21:11 -0700
                Re: Brain teaser for newbies Jukka Lahtinen <jtfjdehf@hotmail.com.invalid> - 2012-06-15 08:14 +0300
                  Re: Brain teaser for newbies Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-15 11:08 -0700
            Re: Brain teaser for newbies Lew <lewbloch@gmail.com> - 2012-06-14 12:43 -0700

#1856 — Brain teaser for newbies

Write a compilable running java class that contains both an abstract
method and a main method.

-- 
Roedy Green Canadian Mind Products
http://mindprod.com
Controlling complexity is the essence of computer programming.
~ Brian W. Kernighan 1942-01-01
.

[toc] | [next] | [standalone]

#1857

On Wednesday, June 13, 2012 1:21:35 PM UTC-7, Roedy Green wrote:
> Write a compilable running java class that contains both an abstract
> method and a main method.

"compilable running"?

Doesn't "running" imply "compilable"?

-- 
Lew

[toc] | [prev] | [next] | [standalone]

#1859

On Wed, 13 Jun 2012 14:15:48 -0700 (PDT), Lew <lewbloch@gmail.com>
wrote, quoted or indirectly quoted someone who said :

>
>Doesn't "running" imply "compilable"?

For a newbie yes, but you can construct class files without writing
Java code.
-- 
Roedy Green Canadian Mind Products
http://mindprod.com
Controlling complexity is the essence of computer programming.
~ Brian W. Kernighan 1942-01-01
.

[toc] | [prev] | [next] | [standalone]

#1860

Roedy Green wrote:
>  Lew wrote, quoted or indirectly quoted someone who said :
>>
>> Doesn't "running" imply "compilable"?
>
> For a newbie yes, but you can construct class files without writing
> Java code.

That is an excellent and subtle point. Thank you.

> Write a compilable running [J]ava class that contains both an abstract
> method and a main method.

A very interesting puzzle. I truly am enjoying it.

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

[toc] | [prev] | [next] | [standalone]

#1865

On Wed, 13 Jun 2012 22:43:36 -0700, Lew <noone@lewscanon.com> wrote,
quoted or indirectly quoted someone who said :

>
>A very interesting puzzle. I truly am enjoying it.

I can think of two basic ways of doing it. One you might discount on
the grounds you would quibble on the meaning of "class".
-- 
Roedy Green Canadian Mind Products
http://mindprod.com
Controlling complexity is the essence of computer programming.
~ Brian W. Kernighan 1942-01-01
.

[toc] | [prev] | [next] | [standalone]

#1867

On 6/14/2012 11:06 AM, Roedy Green wrote:
> On Wed, 13 Jun 2012 22:43:36 -0700, Lew<noone@lewscanon.com>  wrote,
> quoted or indirectly quoted someone who said :
>
>>
>> A very interesting puzzle. I truly am enjoying it.
>
> I can think of two basic ways of doing it. One you might discount on
> the grounds you would quibble on the meaning of "class".


I can think of two ways, one of which has three somewhat minor 
variations, and the other is basically a cheat and has two variations. 
The cheater depends on your definition of "contains."

[toc] | [prev] | [next] | [standalone]

#1866

On Wed, 13 Jun 2012 22:43:36 -0700, Lew <noone@lewscanon.com> wrote,
quoted or indirectly quoted someone who said :

>A very interesting puzzle. I truly am enjoying it.

Professor Melzak (who taught discrete math at UBC) once told us a what
he claimed was a true story.

A prof was writing a proof on the blackboard (a green, erasable
vertical surface on which one wrote with a stick of chalk).

A student stuck up his hand and said, "I don't see how you got from
step 10 to 11".

The prof said "It's trivial".

The student said, "I still don't see it."

The prof stared at it, and stared.  15 minutes went by. He left the
room.  Just as the class was about to dismiss, he returned and said
"It IS trivial".

-- 
Roedy Green Canadian Mind Products
http://mindprod.com
Controlling complexity is the essence of computer programming.
~ Brian W. Kernighan 1942-01-01
.

[toc] | [prev] | [next] | [standalone]

#1868

On 6/14/12 11:14 AM, Roedy Green wrote:
> On Wed, 13 Jun 2012 22:43:36 -0700, Lew<noone@lewscanon.com>  wrote,
> quoted or indirectly quoted someone who said :
>
>> A very interesting puzzle. I truly am enjoying it.
>
> Professor Melzak (who taught discrete math at UBC) once told us a what
> he claimed was a true story.
>
> A prof was writing a proof on the blackboard (a green, erasable
> vertical surface on which one wrote with a stick of chalk).
>
> A student stuck up his hand and said, "I don't see how you got from
> step 10 to 11".
>
> The prof said "It's trivial".
>
> The student said, "I still don't see it."
>
> The prof stared at it, and stared.  15 minutes went by. He left the
> room.  Just as the class was about to dismiss, he returned and said
> "It IS trivial".
>

Unless I'm missing something, this puzzle is trivial.

Perhaps I have confusion over what "running java class" really means? Do 
you mean a class you can start with the "java" command?

[toc] | [prev] | [next] | [standalone]

#1870

On Thu, 14 Jun 2012 12:17:12 -0700, Daniel Pitts
<newsgroup.nospam@virtualinfinity.net> wrote, quoted or indirectly
quoted someone who said :

>Perhaps I have confusion over what "running java class" really means? Do 
>you mean a class you can start with the "java" command?

yes.  I intended this a puzzle for newbies.
-- 
Roedy Green Canadian Mind Products
http://mindprod.com
Controlling complexity is the essence of computer programming.
~ Brian W. Kernighan 1942-01-01
.

[toc] | [prev] | [next] | [standalone]

#1871

Roedy Green <see_website@mindprod.com.invalid> writes:
> On Thu, 14 Jun 2012 12:17:12 -0700, Daniel Pitts

>>Perhaps I have confusion over what "running java class" really means? Do 
>>you mean a class you can start with the "java" command?

> yes.  I intended this a puzzle for newbies.

Hmm, doesn't seem to be much of a puzzle.
There's nothing to stop having a main method and an abstract method in
the same class.

But when I tested this with a simple class, I was surprised to see that
not only did it compile ok, but the jvm didn't even complain about
invoking an abstract class called Test with "java Test".
Now that I thnk about it, it was because I didn't actually try
to instantiate it, the only thing in my main method was a simple
System.out.println call to show that it was executed.
And the next test confirmed this: when I added "Test inst = new Test()",
the compiler showed the expected error message 
"Test is abstract; cannot be instantiated".

-- 
Jukka Lahtinen

[toc] | [prev] | [next] | [standalone]

#1874

On 6/14/12 10:14 PM, Jukka Lahtinen wrote:
> Roedy Green<see_website@mindprod.com.invalid>  writes:
>> On Thu, 14 Jun 2012 12:17:12 -0700, Daniel Pitts
>
>>> Perhaps I have confusion over what "running java class" really means? Do
>>> you mean a class you can start with the "java" command?
>
>> yes.  I intended this a puzzle for newbies.
>
> Hmm, doesn't seem to be much of a puzzle.
[snip]

It is customary to indicate *SPOILER* before giving the solution to a 
problem such as this.

[toc] | [prev] | [next] | [standalone]

#1869

Roedy Green wrote:
> Professor Melzak (who taught discrete math at UBC) once told us a what
> he claimed was a true story.
> 
> A prof was writing a proof on the blackboard (a green, erasable
> vertical surface on which one wrote with a stick of chalk).
> 
> A student stuck up his hand and said, "I don't see how you got from
> step 10 to 11".
> 
> The prof said "It's trivial".
> 
> The student said, "I still don't see it."
> 
> The prof stared at it, and stared.  15 minutes went by. He left the
> room.  Just as the class was about to dismiss, he returned and said
> "It IS trivial".

Every version of that story I've heard over the years was averred to be a 
true story.

-- 
Lew

[toc] | [prev] | [standalone]

Back to top | Article view | comp.lang.java.help

csiph-web