1Usage: jcmd <pid | main class> <command ...|PerfCounter.print|-f file>
2   or: jcmd -l
3   or: jcmd -h
4
5  command must be a valid jcmd command for the selected jvm.
6  Use the command "help" to see which commands are available.
7  If the pid is 0, commands will be sent to all Java processes.
8  The main class argument will be used to match (either partially
9  or fully) the class used to start Java.
10  If no options are given, lists Java processes (same as -l).
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12  PerfCounter.print display the counters exposed by this process
13  -f  read and execute commands from the file
14  -l  list JVM processes on the local machine
15  -? -h --help print this help message
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