AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  operator * cannot be applied          AppletTalk.com Forum Index -> Java Help View previous topic :: View next topic   Author Message George Hester Guest Posted: Sat Apr 03, 2004 4:53 am    Post subject: operator * cannot be applied Here is a piece of CurrencyConvertor.java //private static final double EXCHANGE_RATE = 0.613; try { NumberFormat nf = NumberFormat.getInstance(); double poundValue = nf.parse(amount).doubleValue(); //poundValue *= EXCHANGE_RATE; String rate = getInitParameter("RATE"); poundValue *= rate; RATE is part of a <init-param> element in a web.xml file for my Tomcat Javaserver. <init-param> <param-name>RATE</param-name> <param-value>0.65</param-value> </init-param> If I remove the above comments // and comment the appropriate statements there is no issue. Everything compiles and runs as it should. But as you see it here the CurrencyConvertor.java does NOT compile. The error is: C:Documents and SettingsAdministratorMy DocumentsVisual Studio ProjectsCurr encyConverter>javac CurrencyConverter.java CurrencyConverter.java:31: operator * cannot be applied to double,java.lang.Stri ng poundValue *= rate; ^ 1 error What have I done wrong? J2SDK1.4.2 -- George Hester __________________________________ Back to top Roedy Green Guest Posted: Sat Apr 03, 2004 5:25 am    Post subject: Re: operator * cannot be applied On Sat, 03 Apr 2004 04:53:01 GMT, "George Hester" <hesterloli (AT) hotmail (DOT) com> wrote or quoted : Quote: NumberFormat nf =3D NumberFormat.getInstance(); double poundValue =3D nf.parse(amount).doubleValue(); //poundValue *=3D EXCHANGE_RATE; String rate =3D getInitParameter("RATE"); You are doing something screwy here needlessly encoding your characters. You may have some MIME type option set in a peculiar way. It is pretty hard to figure out what you are talking about with all those =3Ds in there. -- 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 George Hester Guest Posted: Sat Apr 03, 2004 6:13 am    Post subject: Re: operator * cannot be applied That is your newsreader not me. Sorry. George Hester __________________________________ "Roedy Green" wrote in message news:3jis60lkrvu4bcticmjighj79dm2boa81h (AT) 4ax (DOT) com... Quote: On Sat, 03 Apr 2004 04:53:01 GMT, "George Hester" [email]hesterloli (AT) hotmail (DOT) com[/email]> wrote or quoted : NumberFormat nf =3D NumberFormat.getInstance(); double poundValue =3D nf.parse(amount).doubleValue(); //poundValue *=3D EXCHANGE_RATE; String rate =3D getInitParameter("RATE"); You are doing something screwy here needlessly encoding your characters. You may have some MIME type option set in a peculiar way. It is pretty hard to figure out what you are talking about with all those =3Ds in there. -- 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 George Hester Guest Posted: Sat Apr 03, 2004 6:16 am    Post subject: Re: operator * cannot be applied Here's a zip of the question just copied and pasted from the original. It should display correctly in Notpad. -- George Hester __________________________________ "Roedy Green" <look-at-the-website (AT) mindprod (DOT) com> wrote Quote: On Sat, 03 Apr 2004 04:53:01 GMT, "George Hester" [email]hesterloli (AT) hotmail (DOT) com[/email]> wrote or quoted : NumberFormat nf =3D NumberFormat.getInstance(); double poundValue =3D nf.parse(amount).doubleValue(); //poundValue *=3D EXCHANGE_RATE; String rate =3D getInitParameter("RATE"); You are doing something screwy here needlessly encoding your characters. You may have some MIME type option set in a peculiar way. It is pretty hard to figure out what you are talking about with all those =3Ds in there. -- 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 George Hester Guest Posted: Sat Apr 03, 2004 7:03 am    Post subject: Re: operator * cannot be applied No need to check the source. I figured it out. The issue is casting a string to a double. The example I had was incorrect. It was like this: NumberFormat nf = NumberFormat.getInstance(); double poundValue = nf.parse(amount).doubleValue(); String rate = getInitParameter("RATE"); poundValue *= rate; This was wrong. It should be: NumberFormat nf = NumberFormat.getInstance(); double poundValue = nf.parse(amount).doubleValue(); String rate = getInitParameter("RATE"); double dblrate = nf.parse(rate).doubleValue(); poundValue *= dblrate; That casted the string rate to a double dblrate. Which is what the trouble was. George Hester __________________________________ "George Hester" <hesterloli (AT) hotmail (DOT) com> wrote Here's a zip of the question just copied and pasted from the original. It should display correctly in Notpad. -- George Hester __________________________________ "Roedy Green" <look-at-the-website (AT) mindprod (DOT) com> wrote Quote: On Sat, 03 Apr 2004 04:53:01 GMT, "George Hester" [email]hesterloli (AT) hotmail (DOT) com[/email]> wrote or quoted : NumberFormat nf =3D NumberFormat.getInstance(); double poundValue =3D nf.parse(amount).doubleValue(); //poundValue *=3D EXCHANGE_RATE; String rate =3D getInitParameter("RATE"); You are doing something screwy here needlessly encoding your characters. You may have some MIME type option set in a peculiar way. It is pretty hard to figure out what you are talking about with all those =3Ds in there. -- 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 Ryan Stewart Guest Posted: Sat Apr 03, 2004 1:22 pm    Post subject: Re: operator * cannot be applied "Mark Haase" <mehaase (AT) earthlink (DOT) net> wrote Quote: If rate holds a number in it, you'll need to convert it explicitly by using, for instance, String.parseDouble(), before you can perform arithmetic operations with it. Double.parseDouble() ? Back to top George Hester Guest Posted: Sat Apr 03, 2004 3:23 pm    Post subject: Re: operator * cannot be applied I did something like that and fixed it. This was an example verbatum from a book "Tomcat Kick Start" by Martin Bond and Debbie Law. Why do writers of Computer books publish code which doesn't work? George Hester __________________________________ "Mark Haase" wrote in message news:mehaase-701B51.02041203042004 (AT) netnews (DOT) upenn.edu... Quote: In article <Nqrbc.9469$LW2.5478 (AT) twister (DOT) nyroc.rr.com>, "George Hester" <hesterloli (AT) hotmail (DOT) com> wrote: If I remove the above comments // and comment the appropriate statements there is no issue. Everything compiles and runs as it should. But as you see it here the CurrencyConvertor.java does NOT compile. The error is: I doubt this. EXCHANGE RATE is not a valid name for a variable. C:Documents and SettingsAdministratorMy DocumentsVisual Studio ProjectsCurr encyConverter>javac CurrencyConverter.java CurrencyConverter.java:31: operator * cannot be applied to double,java.lang.Stri ng poundValue *= rate; ^ 1 error What have I done wrong? J2SDK1.4.2 Did you even read the error? It says you can't multiply a double times a String...which should be intuitively obvious. If rate holds a number in it, you'll need to convert it explicitly by using, for instance, String.parseDouble(), before you can perform arithmetic operations with it. -- |/| /| |2 | mehaase(at)sas(dot)upenn(dot)edu Back to top Chris Smith Guest Posted: Sun Apr 04, 2004 2:19 pm    Post subject: Re: operator * cannot be applied George Hester wrote: Quote: NumberFormat nf = NumberFormat.getInstance(); double poundValue = nf.parse(amount).doubleValue(); String rate = getInitParameter("RATE"); double dblrate = nf.parse(rate).doubleValue(); poundValue *= dblrate; That casted the string rate to a double dblrate. Just to be picky about terminology; that did not cast the String to a double. Casting a String to a double is, in fact, impossible and always results in a compiler error. What it did was convert a String to a double. The word "cast" -- at least in Java, and in a number of other languages -- refers to a specific piece of language syntax -- namely: ( type ) expr Hopefully, that will save you some confusion in the future. -- www.designacourse.com The Easiest Way to Train Anyone... Anywhere. Chris Smith - Lead Software Developer/Technical Trainer MindIQ Corporation Back to top George Hester Guest Posted: Sun Apr 04, 2004 7:06 pm    Post subject: Re: operator * cannot be applied Thanks Chris. Actually I knew that. I used "Cast" to see if anyone would clarify it for me. I knew I used the expression incorrectly but I didn't know why. Thanks again. George Hester __________________________________ "Chris Smith" wrote in message news:MPG.1ad85d78e3424af69899c6 (AT) news (DOT) pop4.net... Quote: George Hester wrote: NumberFormat nf = NumberFormat.getInstance(); double poundValue = nf.parse(amount).doubleValue(); String rate = getInitParameter("RATE"); double dblrate = nf.parse(rate).doubleValue(); poundValue *= dblrate; That casted the string rate to a double dblrate. Just to be picky about terminology; that did not cast the String to a double. Casting a String to a double is, in fact, impossible and always results in a compiler error. What it did was convert a String to a double. The word "cast" -- at least in Java, and in a number of other languages -- refers to a specific piece of language syntax -- namely: ( type ) expr Hopefully, that will save you some confusion in the future. -- www.designacourse.com The Easiest Way to Train Anyone... Anywhere. 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