Here is the full description J. Bernard :
Classes in <code>com.sun.</code> and <code>sun.</code> packages are considered implementation details, and are not part of the Java API.
They can cause problems when moving to new versions of Java because there is no backwards compatibility guarantee.
Such classes are almost always wrapped by Java API classes that should be used instead.
The following code snippet illustrates this rule:
If this rule doesn't make sense in your context, you just have to deactivate it.