"Package javax.swing doese not exist" Why???

I want to make a java application using JFC.I have imported the package at the beginning of the code.But when I compiled the program,there was a error appears: "Package javax.swing doese not exist".One strange thing is in my java editor , JCreator has set to the right JDK path "C:\Program Files\Java\jdk1.5.0_08\" and I found out that the javax.swing package is still in the JDK with the path "C:\Program Files\Java\jdk1.5.0_08\src.zip".The same thing happen if I use NetBeans also.

Can anybody help? :(