I not only studied Java but also worked with it a good few times. In overall I like the system, my expertise is based upon the following:

• Java SE from 6 upwards...11 as of today
• Persistence(JPA/Toplink) and JDBC
• CDI and other similar goodies
• JSP, JSF and Velocity templates
• Java Swing - though I haven't done that for a while...
• Tomcat and WildFly configurations and management
• NetBeans, Eclipse, IntelliJ...
• GIT Source control management
• ...again...pretty much anything related to this