adam bien's blog

With Bean Managed Concurrency demarcation, the container allows full concurrent access to the Singleton bean instance. It is the responsibility of the bean developer to guard its state as necessary against synchronization errors due to concurrent access. The bean developer is permitted to use the Java language level synchronization primitives such as synchronized and volatile for this purpose. [EJB 3.1 spec, page 111]

@Singleton
@ConcurrencyManagement(ConcurrencyManagementType.BEAN)
public class InefficientHelloWorld {
    //AtomicInteger would be a lot better.
    private static volatile int counter = 0; 
    //synchronized just for demo purposes, o.k with CMT.Bean.
    public synchronized void sayHello(){
        new Thread(new Runnable() {    //still not allowed - but it works
            public void run() {
			  //out.println is not a best practice either...
                System.out.println("Hello World: " + counter++);

            }
        }).start();
    }
}