In spring boot application vary easy to set favicon icon. Here is steps for Spring boot set favicon icon.
Spring Boot looks for a
favicon.ico in the configured static content locations and the root of the classpath (in that order). If such file is present, it is automatically used as the favicon of the application. (Spring Boot favicon.ico document)
NOTE: AFTER UPDATING favicon.ico.OPEN YOUR WEB PAGE AND PRESS CTLR + F5