When Dead Letter Queue becomes a zombie

    Dead Letter Queue (DLQ) defined within JMS provider is known to be a basket for messages that cannot be delivered to a particular destination. A typical scenario is that a DLQ is defined, a consumer of dead messages is attached and everything seems alright. It gives some kind of mental comfort. But is it real?

Why can we use Enums as HashMap keys?

    Last time when I saw enum used as a HashMap key I decided to check why it works out of the box without custom implementations of 'hashCode' and 'equals' methods.

Java EE main method - Hello World application

    Java SE has clearly defined entry point of the program execution - 'public static void main(String[] args)' method. However, when it comes to Java EE such an entry point is blurred. Can we create main method in Java EE?

Simplification with intrinsic locking

    When we deal with concurrency we use 'synchronized' keyword or we leverage the power of java.util.concurrent (JUC) stuff in order to tame our threads. Both of the methods have advantages and disadvantages. I would like to focus on one particular advantage of intrinsic locking.