Explore puzzling Java performance issues and solutions in this 48-minute Devoxx conference talk. Compare newer language features and APIs to their old counterparts, focusing on Java 7, 8, and beyond. Dive into topics such as the Java Measurement Harness (JMH), differences between Java 8 and Java 9+, Compact Strings, StringBuilder's relevance, hot exception throwing, parallel processing for large-scale tasks, and the versatility of VarHandle. Gain insights into the complexities of the JVM and learn how to optimize Java code for better performance.