This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Writing good performance benchmark code in Java is very hard because of the many sophisticated optimizations that the JVM and the JIT do and because of garbage collection, which happens at unpredictable times.
Don't take the results of any micro-benchmark too seriously. Your real, production code might just behave and optimize slightly differently and have different performance characteristics than what you saw in your micro-benchmark.