Integer negation does not give the desired result.

Hey all,

the following code

Code:

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        public static void main(String[] args) {
                System.out.println(50 - 050);
        }

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does not give the desired result

Code:

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0

---

but gives

Code:

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10

---

instead.
Any ideas?

050 is the octal representation of the number 5*8+0*1 == 40. That explains the result.

kind regards,

Jos

you beat me to it!

Oh thanks,

This explains a lot :)

Strange that Java uses a leading 0 instead of an o to express octals. This leads in my opnion to the wrong result because leading 0's in decimal numbers should just be discarded.

Quote:

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Originally Posted by XdaX

Oh thanks,

This explains a lot :)

Strange that Java uses a leading 0 instead of an o to express octals. This leads in my opnion to the wrong result because leading 0's in decimal numbers should just be discarded.

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if you always have a 0 infront of your result somehow and don't want it to use the octals representation. you can always use one of java's methods to cut that off before using it in math expressions.

Quote:

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Originally Posted by XdaX

Strange that Java uses a leading 0 instead of an o to express octals. This leads in my opnion to the wrong result because leading 0's in decimal numbers should just be discarded.

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There's nothing strange about it. Every language needs a way of easily defining octal integers, and this is how it is done with Java. Note that this is for integer constants, something you the programmer have complete control over, so if you understand Java, and code carefully, you should be fine. Also note that where user input is concerned and you parse the integer via Integer.parseInt, a leading 0 will in fact be discarded. Again, you the programmer has complete control over this, and in fact you can parse the number as an octal by simply changing the parser's radix.

Corrections to the above most welcome.

Also, I want to wish a hearty welcome to Jos, a well-known and highly regarded contributer in the Sun Java forums.

It's a C thingy which Java adopted; the reason was that no integral number has leading zeros so a zero introduces an octal number; the 0x or 0X notation is an extension to that lexical rule. They didn't use the 0b or 0B notation for binary numbers ... go and complain at Gosling, Kernighan and Ritchie for that ;-)

kind regards,

Jos

Quote:

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Originally Posted by Fubarable

Also, I want to wish a hearty welcome to Jos, a well-known and highly regarded contributer in the Sun Java forums.

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Thank you very much for the welcome; I just saw that I signed up here more than a year ago but I never posted nor lurked here (until now). I found this forum buried somewhere in my bookmarks ;-)

kind regards,

Jos

I saw that joined date, compared it with the number of posts made and failed to make sense out of anything as well.

Quote:

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Originally Posted by r035198x

I saw that joined date, compared it with the number of posts made and failed to make sense out of anything as well.

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Hi r035198x, I know you too from other forums! I assume it's you, nobody else would come up with a nickname like r035198x ;-)

kind regards,

Jos

Don't make fun of my name.
I'm respected here, see.

Quote:

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Originally Posted by JosAH

It's a C thingy which Java adopted; the reason was that no integral number has leading zeros so a zero introduces an octal number; the 0x or 0X notation is an extension to that lexical rule. They didn't use the 0b or 0B notation for binary numbers ... go and complain at Gosling, Kernighan and Ritchie for that ;-)

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Thanks for the explanation Jos. I think I will have to live with it... But it is not very consistent that leading 0's are accepted for ocals and hexals as

Code:

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int i=00007;
int j=0x007;

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is valid java code :-).

Well for hexadecimal the x must be there so it is different.

Quote:

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Originally Posted by r035198x

Don't make fun of my name.
I'm respected here, [I can't 'post' links here yet ...]

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I read it that you were exceptional in insulting and humiliating beginners ... what did you do? ;-)

kind regards,

Jos

ps. I saw Phil is here as well.

I merely stated some of my special gifts.
When I asked someone to hit their head on a desk I didn't mean to hit it there hard enough so it would crack or anything.


r035198x(<---- Good boy.

Quote:

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Originally Posted by r035198x

I merely stated some of my special gifts.
When I asked someone to hit their head on a des I didn't mean to hit it there hard enough so it would crack or anything.


r035198x(<---- Good boy.

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Tsk, tsk, making fun of innocent stupid newbies; they should be treated with respect and we should do their homework so they can party during the weekends and get a good grade without studying or working for it. Shame on you ;-)

kind regards,

Jos

ps. I removed your links in my reply because this newbie is not allowed to post any links yet ;-)

Quote:

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Originally Posted by JosAH

I read it that you were exceptional in insulting and humiliating beginners ... what did you do? ;-)

kind regards,

Jos

ps. I saw Phil is here as well.

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Yup, hello Jos!

Quote:

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Originally Posted by PhHein

Yup, hello Jos!

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Hi there; how many of the old timers hide in here actually? Am I part of a conspiracy or secret takeover now? ;-)

kind regards,

Jos

A few, pbrockway, Darryl, masijade, camickr.

No conspiracy I know of.

pbrocks away too, DB, camickr ...

Edit: Finally Phil posts earlier than me!