Java concurrency considered underrated

I had interesting mail exchange with my colleague Gilles today. It was about multithreading in Java and how hard is for people to buy into all this.

I would say that the biggest mistake in Java is that it made multithreading to look easy while it is not. Everybody can spawn new threads easily with copy&paste (in the worst case scenario ;-) ). But consequences of incorrect thread-safeness and ignored memory visibility are usually terrible. And it is even worse since introduction of multi core CPUs.

It was about 4 years ago when I was looking for bug in JBoss that caused that an instance of Entity Bean was not saved every 4-6 hours. It took me a week to track it down to incorrect synchronization - two places, one synchronized at instance other at class level. On other side it was rather relaxing - wait till it fails, go through logs, formulate new hypothesis, modify logging in sources, start and wait till another error occurs. Fine for me, but I am not sure about my employer :-) Unfortunately before I could send a patch it was already fixed, so no glory for me :-( ;-) . This example should show how hard it is to fix such a problem and that it happens also to experts occasionally.

Now back to knowledge about Java multithreading. Recently I published my list of influential books. It did not contain anything about particular technology, but I should add following: Brian Goetz: Java Concurrency in Practice. Everybody programming in Java professionally should know its content by heart. There is no better book about this topic.

I believe it is only fair to downgrade to Junior all Senior Java developers not being able to explain how they use multithreading correctly.