AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Long.parseLong() doesn't parse huge long values!!! JDK Bug??          AppletTalk.com Forum Index -> Java Help View previous topic :: View next topic   Author Message Hans Guest Posted: Fri Aug 08, 2003 5:05 pm    Post subject: Long.parseLong() doesn't parse huge long values!!! JDK Bug?? Hello, I have found a very strange bug in JDK 1.4. A huge long constant assignment works fine, but if I want to parse the same huge long as string, it gives an exception. See below! If I remove 1 String digit, it works fine. It seems that parseLong has wrong max value checking? Why doesn't this work and how can I parse legal huge long values? public static void main(String[] args) { // the compiler doesn't complain about this long x = 0xFF7FFFFF80000000L; // but this result in a NumberFormatException long y = Long.parseLong("FF7FFFFF80000000"); } Thanks! Jos Back to top Gordon Beaton Guest Posted: Fri Aug 08, 2003 5:18 pm    Post subject: Re: Long.parseLong() doesn't parse huge long values!!! JDK B On Fri, 8 Aug 2003 19:05:10 +0200, Hans wrote: Quote: Why doesn't this work and how can I parse legal huge long values? public static void main(String[] args) { // the compiler doesn't complain about this long x = 0xFF7FFFFF80000000L; // but this result in a NumberFormatException long y = Long.parseLong("FF7FFFFF80000000"); } Thanks! The number is *larger* than the maximum positive long (x does not contain the value you think it does, it's negative). Have a look at java.math.BigInteger instead. /gordon -- [ do not send me private copies of your followups ] g o r d o n . b e a t o n @ e r i c s s o n . c o m Back to top Chris Smith Guest Posted: Fri Aug 08, 2003 5:47 pm    Post subject: Re: Long.parseLong() doesn't parse huge long values!!! JDK B Hans wrote: Quote: Why doesn't this work and how can I parse legal huge long values? public static void main(String[] args) { // the compiler doesn't complain about this long x = 0xFF7FFFFF80000000L; // but this result in a NumberFormatException long y = Long.parseLong("FF7FFFFF80000000"); } I assume you meant to specify a radix of 16 to parseLong. The reason for the NumberFormatException is that 0xFF7FFFFF80000000 is actually not a valid value for a long. It causes a numeric overflow, and results in a negative number. I just checked the JLS, but didn't off-hand see a section regarding compile-time errors for use of integer literals out of range. I can't say whether the successful parsing of the 'x' line is an error, but I suspect it should be. -- www.designacourse.com The Easiest Way to Train Anyone... Anywhere. Chris Smith - Lead Software Developer/Technical Trainer MindIQ Corporation Back to top pete kirkham Guest Posted: Fri Aug 08, 2003 5:55 pm    Post subject: Re: Long.parseLong() doesn't parse huge long values!!! JDK B Hans wrote: Quote: Why doesn't this work and how can I parse legal huge long values? It's expecting a hex less than max long with a sign indicator, eg: long x = 0xFF7FFFFF80000000L; String str = Long.toHexString(-x); long y = -Long.parseLong("-"+str, 16); To bypass this wierdness, parse in 8 char chunks: y = (Long.parseLong("FF7FFFFF", 16)<<32)| Long.parseLong("80000000", 16); Pete Back to top Roedy Green Guest Posted: Fri Aug 08, 2003 6:02 pm    Post subject: Re: Long.parseLong() doesn't parse huge long values!!! JDK B On Fri, 8 Aug 2003 19:05:10 +0200, "Hans" <nospam (AT) nospam (DOT) com> wrote or quoted : Quote: Why doesn't this work and how can I parse legal huge long values? look at http://mindprod.com/jgloss/primitives.html Longs are SIGNED. Even hex longs are signed. I would guess your long is out of range of SIGNED long. Somebody is being prissy here. I think you can use unsigned hex constants in source codes for int, byte, char, long etc. -- Canadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. Back to top S. Balk Guest Posted: Fri Aug 08, 2003 6:03 pm    Post subject: Re: Long.parseLong() doesn't parse huge long values!!! JDK B Quote: Why doesn't this work and how can I parse legal huge long values? public static void main(String[] args) { // the compiler doesn't complain about this long x = 0xFF7FFFFF80000000L; // but this result in a NumberFormatException long y = Long.parseLong("FF7FFFFF80000000"); } Thanks! The number is *larger* than the maximum positive long (x does not contain the value you think it does, it's negative). Check out Long.MAX_VALUE for the actual maximum value. Quote: Have a look at java.math.BigInteger instead. I think he just needs to know how long works. Back to top pete kirkham Guest Posted: Fri Aug 08, 2003 7:10 pm    Post subject: Re: Long.parseLong() doesn't parse huge long values!!! JDK B Chris Smith wrote: Quote: I assume you meant to specify a radix of 16 to parseLong. The reason for the NumberFormatException is that 0xFF7FFFFF80000000 is actually not a valid value for a long. What about -7 a valid value for a long? long x = -7; String str = Long.toHexString(x); long y = Long.parseLong(str, 16); // throws exception Unfortunately these functions are not inverse str = Long.toString(x, 16); y = Long.parseLong(str, 16); // OK /But/ str is "-7" which is not the normal hex representation of the 64 bit signed integer -7. The hex sequence 0xFF7FFFFF80000000L is a valid long (-36028799166447616). If it were not, the compiler should complain. The long literal section in the java lang spec makes no requirement that hexadecimal is limited to positive or zero longs, and includes the statement: 'The literals 0x8000000000000000L and 01000000000000000000000L are the most negative long hexadecimal and octal literals, respectively. Each has the decimal value -9223372036854775808L' - JLS 3.10.1 The toString, parseLong and decode functions provided for any radix reflect the convention of preprending a negative sign as used in normal decimal representations, so do not correspond to the literal notation for negative hex numbers. Pete Back to top Chris Smith Guest Posted: Fri Aug 08, 2003 7:44 pm    Post subject: Re: Long.parseLong() doesn't parse huge long values!!! JDK B pete kirkham wrote: Quote: Chris Smith wrote: I assume you meant to specify a radix of 16 to parseLong. The reason for the NumberFormatException is that 0xFF7FFFFF80000000 is actually not a valid value for a long. [snip] The hex sequence 0xFF7FFFFF80000000L is a valid long (-36028799166447616). If it were not, the compiler should complain. Sorry for using the "0x" prefix when discussing the actual value. Old habit from somewhere when I'm talking in hex, and it probably was very confusing in this context. I meant to say that the hex number FF7FFFFF80000000 is not a valid value for a long. Yes, apparently the sequence of characters 0xFF7FFFFF80000000L is a valid long literal... I consider that confusing and misleading and a mistake in the language design, but it's true nevertheless. -- www.designacourse.com The Easiest Way to Train Anyone... Anywhere. Chris Smith - Lead Software Developer/Technical Trainer MindIQ Corporation Back to top xarax Guest Posted: Sat Aug 09, 2003 3:52 am    Post subject: Re: Long.parseLong() doesn't parse huge long values!!! JDK B "Hans" <nospam (AT) nospam (DOT) com> wrote Quote: Hello, I have found a very strange bug in JDK 1.4. A huge long constant assignment works fine, but if I want to parse the same huge long as string, it gives an exception. See below! If I remove 1 String digit, it works fine. It seems that parseLong has wrong max value checking? Why doesn't this work and how can I parse legal huge long values? public static void main(String[] args) { // the compiler doesn't complain about this long x = 0xFF7FFFFF80000000L; // but this result in a NumberFormatException long y = Long.parseLong("FF7FFFFF80000000"); } Thanks! Jos Yes, I noticed that parseLong(str,16) doesn't like hex representations that exceed the positive maximum value. I believe, but haven't tested, that you may be able to persuade parseLong(str,16) to work on such strings by prepending a '-' to the string. However, detecting the situation that requires the minus sign is just as much work as parsing the string anyway. I kludged a quick work-around by padding the string out to 16 characters with zeroes on the left, then splitting the string into two 8-character pieces. I parsed each piece, shifted the left piece 32 bits, then merged the results with bit-wise logical OR. Back to top Thomas Gagné Guest Posted: Mon Aug 11, 2003 1:12 am    Post subject: Re: Long.parseLong() doesn't parse huge long values!!! JDK B Why were you using longs in the first place? For you Java programmers, is there a numeric class that will automatically return an integer large enough to represent whatever hex strings you send it? -- ..tom remove email address' dashes for replies opensource middleware at <http://isectd.sourceforge.net> http://gagne.homedns.org Back to top Chris Smith Guest Posted: Mon Aug 11, 2003 3:12 pm    Post subject: Re: Long.parseLong() doesn't parse huge long values!!! JDK B Thomas Gagné wrote: Quote: For you Java programmers, is there a numeric class that will automatically return an integer large enough to represent whatever hex strings you send it? BigInteger. -- www.designacourse.com The Easiest Way to Train Anyone... Anywhere. Chris Smith - Lead Software Developer/Technical Trainer MindIQ Corporation Back to top Tim Tyler Guest Posted: Thu Aug 14, 2003 10:23 am    Post subject: Re: Long.parseLong() doesn't parse huge long values!!! JDK B In comp.lang.java.programmer Chris Smith <cdsmith (AT) twu (DOT) net> wrote: : pete kirkham wrote: :> Chris Smith wrote: :> > I assume you meant to specify a radix of 16 to parseLong. The reason :> > for the NumberFormatException is that 0xFF7FFFFF80000000 is actually not :> > a valid value for a long. :> :> The hex sequence 0xFF7FFFFF80000000L is a valid long :> (-36028799166447616). If it were not, the compiler should complain. : Sorry for using the "0x" prefix when discussing the actual value. Old : habit from somewhere when I'm talking in hex, and it probably was very : confusing in this context. I meant to say that the hex number : FF7FFFFF80000000 is not a valid value for a long. Yes, apparently the : sequence of characters 0xFF7FFFFF80000000L is a valid long literal... I : consider that confusing and misleading and a mistake in the language : design, but it's true nevertheless. I think it's the implementation of Long.parseLong() which is dodgy. Oh well - you can always write a parseLongProperly() method which works with these top-bit-set longs. -- __________ Quote: im |yler http://timtyler.org/ [email]tim (AT) tt1 (DOT) org[/email] Back to top Chris Smith Guest Posted: Thu Aug 14, 2003 4:40 pm    Post subject: Re: Long.parseLong() doesn't parse huge long values!!! JDK B Tim Tyler wrote: Quote: I think it's the implementation of Long.parseLong() which is dodgy. Oh well - you can always write a parseLongProperly() method which works with these top-bit-set longs. I'm curious then: would you want to be able to trest large positive values as negative in ALL bases? That is, would you want to be able to parse decimal 9223372036854775808 and get back -1? Or would you like parseLong to treat certain bases differently? If you're not advocating treating bases differently, then I can understand either choice.. though I would always advocate being error- happy about overflow conditions, Java already ignores overflow in arithmetic, and may as well ignore it in parsing text formats of numbers as well. It was Pete's implication that hex and/or decimal should be somehow different that took me by surprise. The same is the reason I said that I think the literal format is confusing. If I could say 9223372036854775808L and get a valid long (of value -1), then it would at least be consistent and no worse than ignoring arithmetic overflow... but that's not the case. For some reason, 9223372036854775808L is an error, but 0x8000000000000000L is a perfectly valid literal that's equivalent to -0x1. Even more oddly, only one round of overflow is allowed, so 0x10000000000000000L causes an error because it overflows twice, when by all expectations would lead you to believe it would yield 0. Granted, the double overflow is less useful, since allowing single overflow literals could help you pretend that you're working with unsigned variables (as long as you refrain from certain operators). Still, it's a very odd little special case. In any case, it's the inconsistency between bases, and desire for inconsistency between bases, that really feels distasteful to me. -- www.designacourse.com The Easiest Way to Train Anyone... Anywhere. 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