Eclipse did not start as a Java IDE. Eclipse had plug-in support from the beginning. Java may have been one of the first languages supported, but Eclipse supports a variety of languages, including those, for instance, for Web development.
To install Java support, you need to do the following:
Help/install new software
Click on available software sites
Put in the "Work with:" box http://download.eclipse.org/eclipse/updates/4.5.
Atelier uses the Mars platform.
From the check list pick what you want, but be sure for Java Development to click the check box - Java Development tools.
You'll also want to add http://download.eclipse.org/eclipse/updates/4.5. There is an add button on your right.