How about JEdit? the authors of struts in action book have recommended this.
I can understand WebSphere being a server (like Tomcat) but what is build tool? I can't use it to program? then what is the use? I was reading the above mentioned book and it does specified build.xml and stuff but i think it is too lame to design a whole tool just to build a web application? It should have lot of useful features...?
Sure, you are missing something. The purpose of a build tool in a nutshell is to simplify your development, compilation and integration of your app. It is inevitable these days to work without a build tool. We use ANT in one of our projects where we have our development environment set up using eclipse and with the help of ANT, we build it and as a result of that all our files gets stored in the correct location in the web server.
A build tool (like Ant) allows you to "build" your applications.
Using xml you tell it what to do - which files to compile, where to put them, etc. etc. You can set up different "tasks" - ie. 'clean' which could clean out your build directories, 'build' which could compile your code, 'deploy' which could copy your code, etc.
You can even make tasks dependant on other tasks, so you could have a 'full deploy' task that first invokes 'clean', 'build' and then 'deploy'.