It is a bad practice to use Sun's proprietary Java classes?

Question

The compiler display warnings if you use Sun\'s proprietary Java classes. I\'m of the opinion that it\'s generally a bad idea to use these classes. I read this somewhere. Ho

Answer 1

Sun's proprietary Java classes are part of their Java implementation not part of the Java API their use is undocumented and unsupported. Since they are internal they can be changed at any time for any reason that the team working the Sun JVM decides.

Also Sun's Java implementation is not the only one out there! Your code would not be able portable to JVMs from other vendors like Oracle/BEA and IBM.