Using java in FC1(with eclipse)-help needed

[Joe Dumais]

gcj is the java compiler in the gnu suite.
gij is the java executable.  What I have done is to link gij to a file 
called
java.  Then when I type in java somejavabytecode file, I am actually
executing gij, but it runs the same.  For gcj, it is a little more complex
in that the equivalent for javac is "gcj -C" (capital C) which tells gcj to
compile to byte code.  There are other options to gcj that allow compilation
to OS specific binary codes.  You have a few options here, which is to
alias javac to "gcj -C" or to create an executable shell script file called
javac which calls "gcj -C".

Michael Kearey wrote:

> Mark Eggers wrote:
>
>> On Tue, 2004-03-16 at 12:21, fedora-list-request at redhat.com wrote:
>>
>>
>>
>>> Kaustubh Ghosh wrote:
>>
>>
>>
>>> I am quite novice towards java programming in linux.To start with I 
>>> installed  j2re1.4.2_03 and also j2sdk1.4.2_04 in FC1(Both from 
>>> java.sin.com).Now peculiar problems arise.
>>> When I type "java -version" it gives 1.3.1(
>>> When I type "/usr/java/j2sdk1.4.2_04/bin/java -version" it gives 
>>> 1.4.2_04.
>>> Anyway  I  can compile any .java  file with javac.
>>> But when I try to run it with java(any of the above) the gui would 
>>> not come.(Hello World executes perfectly with System.out.println as 
>>> also other non-gui programs).
>>
>>
>>
>> You have both Sun's Java and GNU's Java installed.  GNU's Java comes by
>> default when you select all of the compilers during the install.
>
>
> GNU's Java RPMS for Fedora do not include any 'java' executable. This 
> is what gcc-java package has for executables:
>
> /usr/bin/gcj
> /usr/bin/gcjh
> /usr/bin/jcf-dump
> /usr/bin/jv-scan
>
> And this is what libgcj has :
>
> /usr/bin/gij
> /usr/bin/grepjar
> /usr/bin/jar
> /usr/bin/jv-convert
> /usr/bin/rmic
> /usr/bin/rmiregistry
>
> gij is the bytecode interpretor for GNU java - the equivalent of 
> 'java' executable BTW.
>
>
> I really don't know how you can be so convinced that the java -version 
>  that gives 1.3.1 is anything to do with GNU's java..
>
>>
>> What I did was to find all the matching files in /usr that were supplied
>> by Sun's J2SDK and moved them to a /usr/<directory>/orig.  I then added
>> my $JAVA_HOME/bin and $JAVA_HOME/jre/javaws to my PATH variable.  javaws
>> is where Java WebStart is located.
>>
>> Like you, I have multiple Java versions installed.  I usually keep the
>> current release and the previous release around in case something breaks
>> in the current release that didn't break in the previous release.
>>
>> To do this I make a symbolic link from where I installed Java to
>> /usr/java.
>>
>> For example, if I have j2sdk1.4.2_02 and j2sdk1.4.2_04 installed in
>> /usr, I will link /usr/j2sdk1.4.2_04 to /usr/java.
>>
>> I then set JAVA_HOME to /usr/java.
>>
>> This arrangement seems to work reasonably well.  Another approach would
>> be to not make the link to /usr/java and just set the JAVA_HOME
>> environment variable appropriately.
>>
>> However, in both cases you'll need to take the GNU commands out of your
>> path and make sure that you have the Sun-supplied versions in your path.
>
>
> I'd do 'which java' to see the java executable that is found in path. 
> Also do 'rpm -qa |grep j2'  to see what, if any, RPMS are installed 
> related to java 2...
>
> Yes, and sort out the PATH to have the correct java executable needed..
>
> Cheers,
> Michael
>
>