javap is part of the J2SDK suite tools. it is located in $JAVA_HOME/bin and is a normal utility just like java and javac.
Moreover, TextPad and a DOS console is the best you can hope for as a beginner. That's what I would recommend to any beginner: Your favorite text editor, the J2SE and a terminal. That way you really get a good idea of how Java works. When using IDEs all the dirty work is taken care of by the tool for you and you never know how that compilation/execution stuff works. Way to go