The Java Virtual Machine has a jps tool wich is a bit like the ps command. jps lists all java Processes of a user. You can find the man page at http://java.sun.com/j2se/1.5.0/docs/tooldocs/share/jps.html. I'm using it with the parameters -l (long listing) and -m (arguments) most of the time:

/usr/java/bin/jps -lm

Here are some more examples:

List all java processes: jps

55719 hourglass.jar
51299 jEdit
51610 Main
56026 Jps

Long listing: jps -l

55719 /Users/andreas/.my/pkg/hourglass-0.6.1/lib/hourglass.jar
51299 /Applications/jEdit
56042 sun.tools.jps.Jps
51610 org.netbeans.Main

List arguments: jps -m

55719 hourglass.jar
56051 Jps -m
51299 jEdit 4.2/jedit.jar
51610 Main --userdir /Users/andreas/Library/Application Support/visualvm/1.0.1 --branding visualvm

Java VM parameters: jps -v

56053 Jps -Dapplication.home=/System/Library/Frameworks/JavaVM.framework/Versions/1.6.0/Home -Xms8m
55719 hourglass.jar
51299 jEdit
51610 Main -Djdk.home=/System/Library/Frameworks/JavaVM.framework/Versions/1.6/Home -Dnetbeans.system_http_proxy=DIRECT -Dnetbeans.system_http_non_proxy_hosts= -Dnetbeans.dirs=bin/..//visualvm:bin/..//profiler2: -Dnetbeans.home=/Users/andreas/Downloads/visualvm/platform7 -Dcom.apple.mrj.application.apple.menu.about.name=visualvm -Xms24m -Xmx192m -Dnetbeans.accept_license_class=com.sun.tools.visualvm.modules.startup.AcceptLicense -Dsun.jvmstat.perdata.syncWaitMs=10000