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Java Forum / General / March 2008Determining which versions of java a program will run on?
Is there a way to find this out? Thanks for any advice. Michael Determining which versions of java a program will run on? > Is there a way to find this out? Thanks for any advice. This article may help. Check out class file format. <http://www.javaworld.com/javaworld/javaqa/2003-05/02-qa-0523-version.html> > Is there a way to find this out? Please repeat subject line in the body of the message. What app.? Yours or someone elses? For your own, you might try compiling the code using the -bootclasspath option, and pointing it to the rt.jar of the earlier version. -- Andrew T. PkySci.org > > Is there a way to find this out? > > Please repeat subject line in the body of the message. No problem. > What app.? Yours or someone elses? > [quoted text clipped - 5 lines] > Andrew T. > PkySci.org This is my application. Actually I think I explained it incorrectly. I only want to find out what versions of java the compiled code will run on. I am using 1.6.0_03-b05. I don't intend to recompile it for different versions. Michael ... > > For your own (app), you might try compiling the code > > using the -bootclasspath option, and pointing it > > to the rt.jar of the earlier version. ... > ...I > only want to find out what versions of java the compiled code will run > on. I am using 1.6.0_03-b05. I don't intend to recompile it for > different versions. You don't need to. Any code that is compiled to run on Java 1.4 (for example) will also run just fine in Java 1.5 and 1.6 (etcetera). The -bootclasspath option is useful because it ensures the bytecodes are *really* compatible with the target minimum version, as opposed to simply having the bytecodes written in the form expected for 1.4. That is what Jeff was referring to when he mentioned the class file format. So, it works like this, you compile code using the 1.6 SDK, but specify the -bootclasspath option and point that towards a 1.4 rt.jar (as well, specify the -source and -target, but the -bootclasspath is the one most people miss). The binary will be compatible with 1.4+. Using -bootclasspath is also a good 'acid test' for whether the code is truly compatible with the target minimum version. -- Andrew T. PhySci.org [Snip] > So, it works like this, you compile code > using the 1.6 SDK, but specify the -bootclasspath > option and point that towards a 1.4 rt.jar > (as well, specify the -source and -target, > but the -bootclasspath is the one most people > miss). I'm not the original poster, but I have a related question. You always see the -source and -target options used together and set to the same java version. Is this required these days. What I would like to do is to create a 1.4 class file from 1.6 sources using a 1.4 rt.jar. So I could use modern java language features, but restrict myself to the older libraries and produce a class file that can be read by older versions of the JRE? Am I asking too much here? Thanks.  SignatureKenneth P. Turvey <kt-usenet@squeakydolphin.com> On Mar 10, 10:41 am, "Kenneth P. Turvey" <kt- use...@squeakydolphin.com> wrote: ... > I'm not the original poster, but I have a related question. You always > see the -source and -target options used together and set to the same java > version. You might. I don't. -source never has any meaning below '1.3', whereas the -target might specify '1.1'. >..Is this required these days. What I would like to do is to > create a 1.4 class file from 1.6 sources using a 1.4 rt.jar. So I could > use modern java language features, but restrict myself to the older > libraries and produce a class file that can be read by older versions of > the JRE? I am not entirely sure what you are asking, but note that generics (for e.g.) cannot be used in any code intended to run on 1.4. -- Andrew T. PhySci.org > I am not entirely sure what you are asking, > but note that generics (for e.g.) cannot be > used in any code intended to run on 1.4. Well, that would be one feature I would like. Would this give the modern looping constructs (a favorite of mine)? What about assertions? Thanks? SignatureKenneth P. Turvey <kt-usenet@squeakydolphin.com> On Mar 10, 6:04 pm, "Kenneth P. Turvey" <kt-use...@squeakydolphin.com> wrote: > > I am not entirely sure what you are asking, > > but note that generics (for e.g.) cannot be > > used in any code intended to run on 1.4. > > Well, that would be one feature I would like. Would this give the modern > looping constructs (a favorite of mine)? What about assertions? I do not believe so, though the spec. gurus might be in a better position to advise. (shrugs) I usually 'specify the options and let the compiler decide'. Further, since I only too regularly need to design for binaries that will run on 1.4 or (shock/horror) 1.1, my enthusiasm for the 'new language constructs' has been somewhat lacking. > Thanks? I understand 'Thanks' and 'Thanks!', but what does 'Thanks?' mean? Bear with me - I took the English level in school that was designed for people who's parents were cousins (more interested in math and any flavor of science or tech.). -- Andrew T. PhySci.org On Sat, 8 Mar 2008 08:26:13 -0800 (PST), travel2light <everything2light@yahoo.co.uk> wrote, quoted or indirectly quoted someone who said : >Is there a way to find this out? Thanks for any advice. see http://mindprod.com/project/jdkversion.html -- Roedy Green Canadian Mind Products The Java Glossary http://mindprod.com > Is there a way to find this out? Thanks for any advice. javap -verbose -classpath . yourpackage.YourClass will display major and minor version number. Version X will run on versions >X but not on version <X. Basically JDK version 1.n.x uses major version 44+n. Arne Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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