1. Language
   1. Java 1.4 and before
   2. Java 5 language changes
      1. Generics
      2. "for each" loops
      3. Autoboxing
      4. Varargs
      5. Annotations
   3. Code instrumentation
      1. AOP
      2. Lazy loading
      3. Proxies
   4. Derivatives: mvel, groovy, scala, etc.
   5. Reflection
      1. JavaBean
   6. Design Patterns
2. Persistence
   1. JDBC2,3,4
   2. ORM (Hibernate/JPA, toplink...)
3. Technology Stacks
   1. Apache
   2. Springsource
   3. JBoss
   4. Sun
   5. Oracle
4. Enterprise Architecture
   1. Container
      1. EJB+Web: JBoss, WebLogic, WebSphere, GlassFish
      2. Web: Tomcat, Apache
      3. OSGI: Felix, Equinox
      4. ESB: Mule, ServiceMix, JBoss
      5. IOC: Spring
   2. Transport
      1. RMI (EJB)
      2. HTTP (WS, RS)
      3. MQ (JMS): MQ Series, ActiveMQ, HornetMQ
   3. Business Logic
      1. Rule-based: Drools, JRules
      2. Workflow/BPEL: jBPM, Ode, Camel
   4. Build & Deploy
      1. Zip-based archives: jar, war, ear
      2. Tools: ant, maven
   5. Monitoring
      1. JMX
      2. Logging: log4j, commons
5. Native interface
   1. Shared memory
   2. I/O channels
   3. File locking
   4. JNI
   5. Character sets
   6. Sockets
6. Web
   1. Servlets/JSP
   2. Web Services
   3. Restful Services
   4. JAXB