All the classes in sun.* that accompany the Sun JDK are provided assupport classes that are used to implement specific sets of functionalityfor the core JDK classes. The classes in sun.* such as sun.net.ftp.FTPClientdo not have fixed API’s, nor are they in any way a standard part of theJava language. This means that any application that you write whichuses them may not work with a future JDK version or with a JVM from a vendorother than Sun. To ensure the portability of your programs, you shouldlook at third party Java libraries that provide the same or betterfunctionality. For FTP, an alternative might be to use ORO, Inc’sNetComponents library which is free for most uses and availableat http://www.oroinc.com/.