[java] How to get PID of process I've just started within java program?

I think I have found out a solution, that looks quite bulletproof while working on most platforms. Here is the idea:

1. Create a JVM-wide mutex that you acquire before spawning new process/killing a process
2. Use platform-dependent code to acquire list of child processes + pids of your JVM process
3. Spawn new process
4. Acquire new list of child processes + pids and compare with the previous list. The one that is new is your guy.

Since you check only for child processes, you cannot be wronged by some other process in the same machine. JVM-wide mutex than allows you to be sure, that the new process is the correct one.

Reading child process list is simpler than getting PID from process objects, because it does not require WIN API calls on windows, and, more importantly, it has been done already in several libs.

Below is an implementation of the above idea using JavaSysMon library. It

class UDKSpawner {

    private int uccPid;
    private Logger uccLog;

    /**
     * Mutex that forces only one child process to be spawned at a time. 
     * 
     */
    private static final Object spawnProcessMutex = new Object();

    /**
     * Spawns a new UDK process and sets {@link #uccPid} to it's PID. To work correctly,
     * the code relies on the fact that no other method in this JVM runs UDK processes and
     * that no method kills a process unless it acquires lock on spawnProcessMutex.
     * @param procBuilder
     * @return 
     */
    private Process spawnUDK(ProcessBuilder procBuilder) throws IOException {
        synchronized (spawnProcessMutex){            
            JavaSysMon monitor = new JavaSysMon();
            DirectUDKChildProcessVisitor beforeVisitor = new DirectUDKChildProcessVisitor();
            monitor.visitProcessTree(monitor.currentPid(), beforeVisitor);
            Set<Integer> alreadySpawnedProcesses = beforeVisitor.getUdkPids();

            Process proc = procBuilder.start();

            DirectUDKChildProcessVisitor afterVisitor = new DirectUDKChildProcessVisitor();
            monitor.visitProcessTree(monitor.currentPid(), afterVisitor);
            Set<Integer> newProcesses = afterVisitor.getUdkPids();

            newProcesses.removeAll(alreadySpawnedProcesses);

            if(newProcesses.isEmpty()){
                uccLog.severe("There is no new UKD PID.");
            }
            else if(newProcesses.size() > 1){
                uccLog.severe("Multiple new candidate UDK PIDs");
            } else {
                uccPid = newProcesses.iterator().next();
            }
            return proc;
        }
    }    

    private void killUDKByPID(){
        if(uccPid < 0){
            uccLog.severe("Cannot kill UCC by PID. PID not set.");
            return;
        }
        synchronized(spawnProcessMutex){
            JavaSysMon monitor = new JavaSysMon();
            monitor.killProcessTree(uccPid, false);
        }
    }

    private static class DirectUDKChildProcessVisitor implements ProcessVisitor {
        Set<Integer> udkPids = new HashSet<Integer>();

        @Override
        public boolean visit(OsProcess op, int i) {
            if(op.processInfo().getName().equals("UDK.exe")){
                udkPids.add(op.processInfo().getPid());
            }
            return false;
        }

        public Set<Integer> getUdkPids() {
            return udkPids;
        }
    }
}