I've been searching for the answer daylong, and finally had the problems solved. I am going to write down what I've done to complete them. Hopefully this could help someone.
As far as I know, there is little need to modify PATH on Mac, so here I only tell how to set CLASSPATH on Mac.
1. Temporary setting, which means once you close the Terminal, the setting won't be kept. You have to set again when you open another Terminal.
Here is the steps:
Open the Terminal;
Type:(Here I suppose you put distribution under your username folder)
$export CLASSPATH=${CLASSPATH}:~/jadex-0.96/lib/jadex_rt.jar:~/jadex-0.96/lib/jibx-run.jar:~/jadex-0.96/lib/xpp3.jar:~/jadex-0.96/lib/jadex_standalone.jar:~/jadex-0.96/lib/jadex_tools.jar:~/jadex-0.96/lib/GraphLayout.jar:~/jadex-0.96/lib/jhall.jar
Press return
Then you could check by typing:
$ echo $CLASSPATH to see if you succeed in doing that. After that, you could run command:
$ java jadex.adapter.standalone.Platform
2. Permanent setting.
Open the Terminal
$ ls -a
And see if there is a .bash_profile in your home folder. If there isn't:
$touch .bash_profile
This will create a blank file if there is none. Then,
$open -e .bash_profile
This will open it in TextEdit. Add the following line:
export CLASSPATH=.:/Users/lingao/jadex-0.96/lib/jadex_rt.jar:/Users/lingao/jadex-0.96/lib/jibx-run.jar:/Users/lingao/jadex-0.96/lib/xpp3.jar:/Users/lingao/jadex-0.96/lib/jadex_standalone.jar:/Users/lingao/jadex-0.96/lib/jadex_tools.jar:/Users/lingao/jadex-0.96/lib/GraphLayout.jar:/Users/lingao/jadex-0.96/lib/jhall.jar
save the file
close the Terminal and open a new one
Type:$ echo $CLASSPATH
You will find there are values for CLASSPATH.
Done!