It fails like this:

jstack /java/re/jdk/1.6.0/latest/binaries/solaris-sparc/bin/java core.7501
Usage:
    jstack [-l] <pid>
        (to connect to running process)
    jstack -F [-m] [-l] <pid>
        (to connect to a hung process)
    jstack [-m] [-l] <executable> <core>
        (to connect to a core file)
    jstack [-m] [-l] [server_id@]<remote server IP or hostname>
        (to connect to a remote debug server)

Options:
    -F to force a thread dump. Use when jstack <pid> does not respond (process is hung)
    -m to print both java and native frames (mixed mode)
    -l long listing. Prints additional information about locks
    -h or -help to print this help message
-------------------
It works ok when the -F option is used, eg
    jstack -F .../bin/java corefile


###@###.### 2005-07-15 18:00:06 GMT