Dive into the intricacies of Java bytecode and code coverage in this comprehensive conference talk from GOTO Copenhagen 2023. Explore how different compiler versions transform source code, focusing on the implementation details of JaCoCo, the popular open-source code coverage tool for Java. Learn about bytecode pattern matching, compiler-generated artifacts, and the challenges of achieving full code coverage. Discover how JaCoCo filters out unnecessary elements and handles synthetic methods. The presentation includes a practical demo and covers topics such as Java, bytecode, enums, and the intricacies of Java code coverage. Gain valuable insights into the inner workings of class files and improve your understanding of Java bytecode manipulation.