In this section, we will list three technologies:

• Java agent
• Polyglot programming
• Annotation processing

Knowing them is not a must for a Java professional. Knowing about them is. Java agents are used mainly in development environments and in operation. They are complex runtime technologies that interact with the already running JVM. Annotation processing is the other end. Annotation processors are plugged into the Java compiler. Polyglot programming is in the middle. It is JVM programming, just like programming in Java, but by using some different language or, perhaps, some different language and Java together. Or even many languages, such as Jython, Groovy, Clojure, and Java together.

We will discuss these technologies so that we will get some idea about what they are and where to look for further information in case we want to learn more about them.