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Java Forum / General / May 2005java 1.5 on 1.4.2
Just need to verify something. You can not use a java 1.5 war file on a machine with java 1.4.2 loaded on it. Is this not right??? Thanks Yeah the compiled .class files shouldn't match. oracle schreef: > Just need to verify something. > > You can not use a java 1.5 war file on a machine with java 1.4.2 loaded > on it. That depends, you can compile Java 1.5 source code to a 1.4 class file. Then it will run fine on a java 1.4.2 JVM, even with the use of generics, and other java 1.5 extensions. > oracle schreef: > > Just need to verify something. [quoted text clipped - 5 lines] > Then it will run fine on a java 1.4.2 JVM, even with the use of > generics, and other java 1.5 extensions. Hmm, I'd like a copy of your JVM... You can specify to javac the Source Code and Target JVM versions you require. Specifying a lower Target requires also that you set a lower Source. So you can compile, for example, for 1.4, using: javac -source 1.4 -target 1.4 MyClass.java However, if MyClass.java uses *any* JDK 1.5 specific features (Generics, For-each loop, etc), you'll get: MyClass.java:5: generics are not supported in -source 1.4 (try -source 1.5 to enable generics) static Vector<MyClass> v = new Vector<MyClass>(); ^ 1 error (as already mentioned, the -source argument is mandatory in this case, although I'm not sure if it implies the target). Ross  Signature[Ross A. Bamford] [ross AT the.website.domain] Roscopeco Open Tech ++ Open Source + Java + Apache + CMF http://www.roscopec0.f9.co.uk/ + info@the.website.domain > MyClass.java:5: generics are not supported in -source 1.4 > (try -source 1.5 to enable generics) > static Vector<MyClass> v = new Vector<MyClass>(); Why not try -source 1.5 -target 1.4? > > MyClass.java:5: generics are not supported in -source 1.4 > > (try -source 1.5 to enable generics) > > static Vector<MyClass> v = new Vector<MyClass>(); > > Why not try -source 1.5 -target 1.4? Why don't you? :) Quote: "javac: source release 1.5 requires target release 1.5" You have to understand that Java isn't Perl - it's not interpreted. New *language* features introduce new *opcodes* which a 1.4 JVM would probably class as Invalid (look at ClassLoader/SecurityManager). Javac obviously won't let you specify 'Generate these special 1.5 Opcodes, and then target them for a JVM that's never heard of them". Cheers, Ross Signature[Ross A. Bamford] [ross AT the.website.domain] Roscopeco Open Tech ++ Open Source + Java + Apache + CMF http://www.roscopec0.f9.co.uk/ + info@the.website.domain > You have to understand that Java isn't Perl - it's not interpreted. New > *language* features introduce new *opcodes* which a 1.4 JVM would > probably class as Invalid (look at ClassLoader/SecurityManager). I'm not aware of any new opcodes being introduced in a long time. There is one new variation on the ldc instruction in java 1.5, which however does not do anything that couldn't be done before (it loads a class literal.) It is however impossible to compile all 1.5 source to 1.4 bytecode. The most obvious problems are lack of an annotation specification in the 1.4 class file format, and also the need for generic signatures, also not present in 1.4. SignatureDaniel Sjöblom Remove _NOSPAM to reply by mail On Fri, 2005-04-29 at 13:42 +0300, Daniel Sj=B6blom wrote: > I'm not aware of any new opcodes being introduced in a long time. Of course you're right - I said it without thinking, just to try to get across why it doesn't work. The intent remains the same, that the core JVM doesn't understand the class file structure. Sorry for confusion :) Signature[Ross A. Bamford] [ross AT the.website.domain] Roscopeco Open Tech ++ Open Source + Java + Apache + CMF http://www.roscopec0.f9.co.uk/ + info@the.website.domain Ross Bamford <ross@read.the.sig> said: >You have to understand that Java isn't Perl - it's not interpreted. Apologies for taking this completely off-topic, but just for the record, Perl isn't interpreted, either - it's compiled into bytecode, but the compilation results are not (normally) permanently stored. Instead, there's a compilation phase each time you run a Perl program. From documentation: After locating your program, Perl compiles the entire program to an internal form. If there are any compilation errors, execution of the program is not attempted. (This is unlike the typical shell script, which might run part-way through before finding a syntax error.) SignatureWolf a.k.a. Juha Laiho Espoo, Finland (GC 3.0) GIT d- s+: a C++ ULSH++++$ P++@ L+++ E- W+$@ N++ !K w !O !M V PS(+) PE Y+ PGP(+) t- 5 !X R !tv b+ !DI D G e+ h---- r+++ y++++ "...cancel my subscription to the resurrection!" (Jim Morrison) Tor Iver Wilhelmsen schreef: >>MyClass.java:5: generics are not supported in -source 1.4 >>(try -source 1.5 to enable generics) >> static Vector<MyClass> v = new Vector<MyClass>(); > > Why not try -source 1.5 -target 1.4? I use these paramaters, and it works fine. Maybe it doesn't work for all 1.5 extensions, but it works fine for generics. > I use these paramaters, and it works fine. Maybe it doesn't work for all > 1.5 extensions, but it works fine for generics. What does "javah -version" say? [Or "javac -version" if javac now does -version]. > Tor Iver Wilhelmsen schreef: > > [quoted text clipped - 6 lines] > I use these paramaters, and it works fine. Maybe it doesn't work for all > 1.5 extensions, but it works fine for generics. No, you cannot use -source 1.5 -target 1.4. You want to look at the undocumented compiler switch -jsr14. If you are using source level 1.5, why are you using a data type (java.util.Vector) that was obsoleted 7 or 8 years ago? http://qa.jtiger.org/GetQAndA.action?qids=53 SignatureTony Morris Software Engineer, IBM Australia. BInfTech, SCJP 1.4, SCJD http://www.jtiger.org/ JTiger Unit Test Framework for Java http://qa.jtiger.org/ Java Q&A (FAQ, Trivia) http://xdweb.net/~dibblego/ 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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