``++private++`` classes that are never used are dead code: unnecessary, inoperative code that should be removed. Cleaning out dead code decreases the size of the maintained codebase, making it easier to understand the program and preventing bugs from being introduced.
=== Noncompliant code example
[source,text]
----
public class Foo
{
...
private class MyUnusedPrivateClass {...} // Noncompliant
