$HOME/.gradle holds all the jars from all previous downloads.
 When you turn on debug, you can see the actual download : gradle build –debug.
 Note IDE java editor can use version 123 of a jar for syntax check, but the command line compilation can use version 124 of the jar. This is very common in all IDEs.
When I make a change to a gradle config,
- Intellij prompts for gradle import. This seems to be unnecessary re-download of all jars — very slow.
- Therefore, I ignore the import. I think as a result, Intellj java editor  would still use the previous jar version as the old gradle config is in effect. I live with this because my focus is on the compilation.
- For compilation, I use the grade “build” action (probably similar to command line build). Very fast but why? Because only one dependency jar is refreshed 
- Gary used debug build  to prove that this triggers a re-download of specific jars iFF you delete the jars from $HOME/.gradle/caches/modules-2/files-2.1
 For a given dependency jar, “refresh” means download a new version as specified in a modified gradle config.
— in console, run
gradle build #there should be a ./build.gradle file