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.

Database deadlock example

    Some time ago I wrote about deadlock in Java language. However the problem of a deadlock can also appear in a database. The transactions are just the analogues of threads. Is a database able to recover from a deadlock? Let's check this out!

Simple deadlock example - jstack to the rescue

    The most popular deadlock example is about acquiring two different locks in the opposite order by two different threads. However it can be tricky to obtain deadlock in that way because we must encounter unlucky timings of the threads. I created a piece of code that is very likely to result in a deadlock.