In JDK 8 jps will display output that looks like this:

$ jps
2349 Jps
26941 TTY

In JDK 9 - after jigsaw - it will display something like this

$ jps
2467 sun.tools.jps.Jps
26941 com.sun.tools.example.debug.tty.TTY

The reason is that the format for the sun.java.command property has changed after jigsaw. If the main-class is in a class in a module, the property will look something like "jdk.jdi/com.sun.tools.example.debug.tty.TTY" (with the module added to the front).

sun.jvmstat.monitor.MonitoredVmUtil.mainClass() will fail to parse this new format and returns the full class name including package.

I wonder if there are other uses of sun.java.command that also has problems.