I downloaded commons-net-3.0.1-bin.zip file and extracted it to java lib folder. I have set the path to java bin folder and classpath=.;C:\Program Files\Java\jdk1.7.0_01\lib\commons-net-3.0.1.
commons-net-3.0.1 folder has  commons-net-3.0.1 jar , commons-net-3.0.1-sources.jar  and  commons-net-examples-3.0.1.jar files.
In my program I imported org.apache.commons.net.ntp.* package, and it gave the "package doesn't exist" error.
 
     
     
    