Today's Java developers fall roughly into three categories: architects and modelers who work from diagramming levels; Web-facing developers, who work primarily with JSP, Struts, and JSF (JavaServer Faces) technologies or their equivalents; and straight-ahead developers, who work mostly in pure code.
The last group is particularly well suited to the Eclipse IDE (free and open-source, available at eclipse.org), which provides technology closely attuned to the coding experience. With Eclipse, pure-code programmers will find considerable functionality, a large and active community, and many resources to maximize their productivity.
Nonetheless, the Eclipse interface is not intuitive, and it takes practice to navigate comfortably. (Eclipse, from O’Reilly & Associates, serves as a great manual during this learning period, by the way.) For functionality comparable to Eclipse, but with an easier interface and a low price, I suggest looking at IntelliJ IDEA from JetBrains, which presents an excellent alternative that should be evaluated by any site considering adoption of Eclipse for Java development. Either way, you will secure a tool that is the envy of all other language developers.