Servlet

Servlet is a small program that executes on the server. Just as applets dynamically extend the functionality of a web browser, servlets dynamically extend the functionality of a web server. It is helpful to understand that as useful as applets can be, they are just one half of the client/server equation. Not long after the initial release of Java it became obvious that Java would also be useful on the server side. The result was the servlet. 

Thus, with the advent of the servlet, Java spanned both sides of the client/server connection. Although the creation of servlets is beyond the scope of this beginner’s guide, they are something that you will want to study further as you advance in Java programming. (Coverage of servlets can be found in my book Java: The Complete Reference, published by Oracle Press/McGraw-Hill.) compilation. 

The remaining code is simply interpreted. However, the just-in-time approach still yields a significant performance boost. Even when dynamic compilation is applied to bytecode, the portability and safety features still apply because the JVM is still in charge of the execution environment.