1. You need jdk-1_5_0-doc.zip and src.zip; If you don't have them,
download them from sun's site http://java.sun.com/j2se/1.5.0/download.jsp
2. Eclipse: Windows -> Preferences -> Java -> Installed JRE's , check
and select jre1.5.0_06 press Edit... and the "Edit JRE" window pops up.
3. In the "Edit JRE" window uncheck "Use default system libraries"
4. In the list expand the "rt.jar" entry
5. Select "Source attachement" , press Edit and enter the full path to
the "src.zip" file (eg: C:/Program Files/Java/jdk1.5.0_06/src.zip )
6. Select "Javadoc location", press Edit and enter the full path to the
"jdk-1_5_0-doc.zip" file
To see a simplified Javadoc explanation when you hover your mouse over a
class/method you need only the source code to be installed (that is
src.zip). Of course, if you install Javadoc too, as described above, you
can get more detailed using SHIFT+F2.