What does "pinned" icon of a class in Intellij IDEA mean?

Question

org.apache.commons.validator.routines.CodeValidator class of Apache Commons Validator library is presented as "pinned class" icon. What does it mean? I don't see any unusual things it this class.

Answer 1

According to this, the "pinned" symbol represents a final Java class. As you can see with the link you provided, the CodeValidator class is, indeed, final.