For OpenJDK, startup time appears to be dominated by the number of classes loaded[0]. I was told that .class files are read out of the JAR files one at a time,

For OpenJDK, startup time appears to be dominated by the number of classes loaded[0]. I was told that .class files are read out of the JAR files one at a time, rather than being slurped into memory in a batch and then processed. I'd be interested in seeing whether that holds true for OpenJ9. [0] https://github.com/dsyer/spring-boot-startup-bench/tree/master/static https://github.com/dsyer/spring-boot-startup-bench/tree/mast...