public static void main(String args[])throws java.io.IOException{
}
THAT will never work.
You should use a IDE like Eclipse or Netbeans, those will probably notify you that the lib is not there. And check if the lib including "JpcapCaptor" is listed to be included for the build.
Also please separate the application from the main. The main-function is just the entry point, please let that one call some object and fire that Object up. Java is OOP, not some script.