You might be thinking, why should a Java developer read a book on Performance tuning? When I first faced this question a long time back, I thought I will do it later, but I never got back to that for a long time. I realize my mistake of having a lack of knowledge on memory measurement, JVM tuning, and finding bottleneck only when I faced severe performance and scalability issues on our mission-critical, server-side financial application written in Java. It's true that when you really need it, you learn most, but those times are not the best time to learn fundamentals, in fact, those times are to apply and correct your misunderstanding.