Eclipse has views and perspectives(1) as the top level components for presenting visual information to a user. It is easy to get the Eclipse layout back to where you where. You probably spend most of your time in the Java Perspective, If you end up with an odd view like the first image below. You can easily go back to the Java View by clicking the very small Java View Button/Tab in the upper right hand corner.
(1) What is the difference between a view and a perspective? Views are usually the smaller windows in a perspective. In the image directly above we have a package view in a Java Browsing perspective