Using java in FC1(with eclipse)-help needed

[Kaustubh Ghosh]

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).

I also installed eclipse sdk.It created a directory "eclipse" under /opt.When 
I cycled to the directory and typed "eclipse" I got messages
"
warning:cannot determine -os type
warning:cannot determine -ws type.
warning:cannot determine -arch type.
warning:cannot determine -showsplash type.
"
After a while it gives an error(in a gui):
"Error:Java (VM) had to be shut down:Exit Code=1
/usr/bin/java
-cp /opt/eclipse/startup.jar org.eclipse.core.launcher.Main
-os linux
-ws gtk
-arch x86
-showsplash /opt/eclipse/eclipse_showsplash 600
"

Cannot make any head or tail of it.
I also tried to install Netbeans developer using "nbdx2_21.class" file by 
giving command "java nbdx2_21".What I got was:
"Exception in thread "main" java.lang.NoClassDefFoundError: nbdx2_21"

Can I get any help?Thanks in advance.