Prevent multiple JVM to access concurrently the same file

sync.groovy

import java.nio.channels.FileLock

final file = new RandomAccessFile(new File("foo.lock"), "rw")
println "<Entering in critical section>"
try {
    /* 
     * wait to acquire a lock 
     */
    def secs = 0
    FileLock lock
    while( !(lock=file.getChannel().tryLock()) )  {
        print "\rwaiting to acquire lock ${(secs+=100).intdiv(1000)  } "
        sleep 100
    }
    /* 
     * now it can do the job
     */
    println '\r'
    try {
        int count = 20
        while( count>0 ) {
            print "\rtime to finish job .. ${count--} "
            sleep 1_000
        }
        println ""
    }
    finally {
        lock.close()
    }
}
finally {
    file.close()
}
println "Done"