This program has two threads: Even and Odd to print Even and Odd numbers.

Run the program and also make a profiling recording.

java -Xms64m -Xmx64m -XX:+UnlockDiagnosticVMOptions -XX:+DebugNonSafepoints -XX:+FlightRecorder -XX:StartFlightRecording=settings=profile,duration=30s,name=Latencies,filename=latencies.jfr -Xlog:jfr=info -jar target/latencies.jar

In Threads -> Latencies tab, you should see that the program has many blocked events.

You should also see red blocks in Events -> Graph tab. Red blocks are not good as the thread is just waiting to acquire a lock.

See Threads -> Contention tab to see the Locks and also see Threads -> Lock Instances to check whether both threads share the same lock instances.

Since there is no shared resource to protect, you can avoid the synchronized keyword and improve the performance.

Try the program again after removing the synchronized keyword in isEven method.