Rename the file spring-cloud-huawei-servicecomb-discovery-1.6.1-Finchley-javadoc.jar to spring-cloud-huawei-servicecomb-discovery-1.6.1-Finchley-javadoc.zip
Use your favourite unzip tool (WinRAR / WinZIP) to extract it, now you have a folder spring-cloud-huawei-servicecomb-discovery-1.6.1-Finchley-javadoc
Double click index.html will open the index page on your default web browser.