java is a platform independant language

but when i compile my program on xp or fedora8 it worked only on xp and fedora8 but not mac
also i tried it on an older xp machine and it didn't work

when i compiled it on mac it worked on mac and xp but didn't try it on older xp yet

this seems to be a issue with some version number
only thing i saw was maybe multiple jre's installed or compiled with different versions ???

i dunno
it is kinda lame ... i thought java worked anywhere but i had to do a little work to make this so

i had to get my hands on a mac and compile code there then when i made jar file it seems to work everywhere

also when i try to double click my executable jar file in linux
fedora 8
it seems to treat it just like a archive file like a zip
why didn't it run the program
and how would i make it an application for linux
and why does it only seems to be platform independant when complied w/ mac

I would start by running:

on all your machines. Java is mostly backwards compatible, but not forwards. If you compile some source with a Java 6 compiler, it won't run on a Java 5 runtime.

when i can get to them i will
just a little lame - this issue is mucking up one of the beauties of the language

java -version = 1.6.0_03 on this xp laptop
i downloaded it not too long ago and on fedora8 i used whatever comes with eclipse on the install dvd
as far as my families mac's ... hell i dunno whatever comes with them
my dads is new and mom and sisters are older

i assume this laptop is newer than most if not all of the other machines so i don't get it ... i guess that word MOSTLY backwards compatible is the key

why would 6 not run on 5 ... isn't that what backwards compatible means

You can compile with a newer version code that can run on an older JVM. Just use the "-target" option. eg: javac -target 1.4 ...

ok but would that be equal to compiling with that version
or does that make it backwards compatable
like ... do i lose the ability to now run with the newer version i have

say i run this from my xp laptop that has 1.6 i guess
javac -target 1.4 Program.java
then will it run only on 1.4 or will it work on 1.6 and 1.4
know what i am asking . . .

wait i think i get it
it needs to be compiled w/ oldest version to work on them all

if compiled w/ 1.6 it will only work for 1.6
if compiled with 1.5 it will work for 1.5 and 1.6 machines
if compiled on 1.6 with 1.4 -target switch it will work w/ 1.4 and greater

am i understanding it ?

That's it.
Use a 1.6 javac with -target 1.4 and your class will be runnable by 1.4, 1.5, 1.6, 1.7 and so on.

Hi -

You've got a couple of different problems here:

1. You seem to think double-clicking on a .jar should run it as a program

Granted, that might be convenient in some cases. It might be downright annoying in other cases. What if you need multiple .jars? What if you have multiple different "main()" entries? What if you just want to look at the contents of a resource .jar? What if it's malicious? Etc etc ad nauseum...

Bottom line: nobody says it has to work this way; and, more often than not, it simply *doesn't*.

2. You are correct: your Java Runtime must be greater than or equal to the Java version that the .class files in the .jar were compiled under.

There are many ways to achieve this.

For example, you can make sure the latest/greatest runtime is loaded. You can install *multiple* runtimes (and switch between them with a simple environment setting, like $JAVA_HOME, or changing your -classpath). Or you can explicitly tell a new compiler to write .class files compatible with an older version (e.g. -target).

'Hope that helps .. PSM

I had the same problem and yes the target was the problem, I wish I had seen this before.

Regards.

paul

what do you recommend then
java doesn't compile into any executable format
executable jar seems the best
all you have to do it double click and it runs the program
just run jar xvf filename.jar to extract it

my dads mac has this cool xcode developer tools that can make .app files from java files

seen things like this for windows but they seem to cost money

i made a sudoku game for my grandma and this seems to be the best way to give it to her ... all she has to do it get one file and double click it