kill -3 to get java thread dump
You could alternatively use jstack (Included with JDK) to take a thread dump and write the output wherever you want. Is that not available in a unix environment?
jstack PID > outfile
The thread dump is written to the system out of the VM on which you executed the kill -3. If you are redirecting the console output of the JVM to a file, the thread dump will be in that file. If the JVM is running in an open console, then the thread dump will be displayed in its console.