Eclipse is an free IDE originally donated to the community by IBM. It has become the most dominant IDE for developing Java applications as well as applications in other laguages. Sun and Microsoft have alternative IDEs but Eclipse has attracted the the largest following.
Install the Callisto version of Eclipse for Java development. It contains all of the plug-ins for Java development including Web Tools Platform which we need.
Eclipse does not have any environment variables of its own but does want to find "JAVA_HOME" which should point to your version of Java.
If you start Eclipse and it runs, you have a good installation. If not, refer to the Eclipse Site for help.
The Callisto version of Eclipse should contain the WTP(Web Tools Platform) plug-ins. They show up in the list of plug-ins as individual items:
If you are missing the any of the Eclipse Web Tools platform compents, you can download them from the Eclipse site