What are the containers in Java

You can check at official Sun tutorial.

EDIT

Check also the Google Collections library:

The Google Collections is a set of new collection types, implementations and related goodness for Java 5 and higher, brought to you by Google. It is a natural extension of the Java Collections Framework you already know and love.

Edit: There was a very nice cheatsheet for Java Collections which is not available anymore. There are lots of others though, like this one.

Have a look-see at the Java Collections API, and at this page for more information

Essentially, all the docs about java "containers", or better known as collections, is here, with the most useful page being this one, brief list here. There are other implementations of the collections framework, like the fastutils framework that gives better performance if you knew the type you were going to use. Also Gnu Trove is another one similar to fastutils.

"Containers are the interface between a component and the low-level platform-specific functionality that supports the component. Before a web component, enterprise bean, or application client component can be executed, it must be assembled into a Java EE module and deployed into its container." here is my source : http://docs.oracle.com/javaee/1.4/tutorial/doc/Overview3.html