Rename the file example-number-guessing-game-es-mongodb-spring-blocking-0.16.6-javadoc.jar to example-number-guessing-game-es-mongodb-spring-blocking-0.16.6-javadoc.zip
Use your favourite unzip tool (WinRAR / WinZIP) to extract it, now you have a folder example-number-guessing-game-es-mongodb-spring-blocking-0.16.6-javadoc
Double click index.html will open the index page on your default web browser.
