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Java Forum / General / June 2007method compareTo
Hi, I've read the API description of compareTo method but I don't understand how is calculated the returning value when strings aren't equals! Any more simple explanation? Thanks. >Hi, I've read the API description of compareTo method but I don't >understand >how is calculated the returning value when strings aren't equals! > >Any more simple explanation? Why not try experimentation?  SignatureAndrew Thompson http://www.athompson.info/andrew/ > >Hi, I've read the API description of compareTo method but I don't > >understand [quoted text clipped - 8 lines] > > Message posted via JavaKB.comhttp://www.javakb.com/Uwe/Forums.aspx/java-general/200706/1 Yes I made it but in some examples I don't understand the result. String a = "I am a string!"; String b = "i am a string!"; int rp = a.compareTo(b); // -32 here rp is -32 and for understanding that value I must check the correspondent Unicode different values?? josh skrev: >>> Hi, I've read the API description of compareTo method but I don't >>> understand [quoted text clipped - 15 lines] > here rp is -32 and for understanding that value I must check the > correspondent Unicode different values?? Unicode, ASCII, iso-8859-1, whatever... The value of 'I' is 32 less than 'i' in any case. The difference is negative, which is the information you need for sorting. Thus the first character values in the two strings that differ determine the relation. > Hi, I've read the API description of compareTo method but I don't > understand > how is calculated the returning value when strings aren't equals! > > Any more simple explanation? Think about the simplest possible algorithm for determining whether two strings are equal, and the difference function it would lead to.. On 14 Giu, 10:14, "Mike Schilling" <mscottschill...@hotmail.com> wrote: > > Hi, I've read the API description of compareTo method but I don't > > understand [quoted text clipped - 4 lines] > Think about the simplest possible algorithm for determining whether two > strings are equal, and the difference function it would lead to.. I learned it use lexicographic algorithm ... it mean that if I have: String s = "a"; String t = "g"; than s.compareTo(t) return -6 because g is far 6 letters from a .... but why -32 in my examples ??? > On 14 Giu, 10:14, "Mike Schilling" <mscottschill...@hotmail.com> > wrote: [quoted text clipped - 13 lines] > than s.compareTo(t) return -6 because g is far 6 letters from a .... > but why -32 in my examples ??? As someone said... ASCII, ISO-xxx, whatever. All assigns a numerical position to the characters in the charset. Take a look at an ASCII table (http://www.asciitable.com/) and count, and you will see that just like "g" it 6 letters higher that "a", You will see that "i" is 32 letters higher than "I". SignatureDag. > > On 14 Giu, 10:14, "Mike Schilling" <mscottschill...@hotmail.com> > > wrote: [quoted text clipped - 23 lines] > -- > Dag. yes I have read an ASCII table in a wrong way! >>> On 14 Giu, 10:14, "Mike Schilling" <mscottschill...@hotmail.com> >>> wrote: [quoted text clipped - 20 lines] > > yes I have read an ASCII table in a wrong way! Actually ASCII values do not matte at all here - the exact return value is just an implementation detail. The important bit is the information that the return value is less than, equal to or greater than zero which is mandated by the contract of Comparable. If you want to know how it's implemented in the case of String you can look into the sources of the std lib. It's all there. Kind regards robert > Hi, I've read the API description of compareTo method but I don't > understand [quoted text clipped - 3 lines] > > Thanks. lexicographical order (like dictionary or telephone book) | > Hi, I've read the API description of compareTo method but I don't | > understand [quoted text clipped - 5 lines] | > | lexicographical order (like dictionary or telephone book) Dictionary order (and most text ordering) is case-insensitive, not lexicographical which is strictly by comparison of each character. Matt Humphrey matth@ivizNOSPAM.com http://www.iviz.com/ > Dictionary order (and most text ordering) is case-insensitive, not > lexicographical which is strictly by comparison of each character. Dictionary doesn;t ignore case; what it does is make case the least significant difference. That is, instead of the Unicode ordering ...ABC...XYZ...abc./.xyz... dictionary order is ...AaBbCc...XxYyZz.... | > Dictionary order (and most text ordering) is case-insensitive, not | > lexicographical which is strictly by comparison of each character. [quoted text clipped - 7 lines] | | ...AaBbCc...XxYyZz.... I see what you mean. Google turned up many different ways for ordering dictionaries and phone books. Here's what Sybase means by "dictionary order". http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.dc38421_1500/html/ ntconfig/ntconfig86.htm and there are also special orderings for phone books. "Dictionary order" depends on whose dictionary you're talking about and is rarely ever the natural lexicographical order of the characters. Matt Humphrey matth@ivizNOSPAM.com http://www.iviz.com/ Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. 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