Do you know what is inside of your class files? Are you ready to bet? Let's have fun by diving into bytecode pattern matching and explore how different compilers (Java/Kotlin) and their different versions, from the old ones up to the most recent, transform your source code.

Our dive will be based on details of the implementation of the most popular open-source code coverage tool for Java – JaCoCo ( https://www.jacoco.org/ ), which finds in bytecode and filters out various compiler generated artifacts, which otherwise require unnecessary and sometimes impossible tricks to have full code coverage.

New JVM features now arrive with each JDK release. If you are interested to learn and try these new features and wanna know-how in case of problems investigate and report JVM crashes, then come to listen about its new feature introduced in Java 11 - Constant Dynamic. During this talk, we'll see what actually means dynamic constant and why it is such a powerful addition to JVM. We'll also see how little holes in implementation were causing JVM crashes in OpenJ9 and OpenJDK 11-14, and how by developing JaCoCo we find and report such bugs - you also can!