Things you can mark as static:
■ Methods
■ Variables
■ A class nested within another class, but not within a method .
■ Initialization blocks

Things you can't mark as static:
■ Constructors (makes no sense; a constructor is used only to create instances)
■ Classes (unless they are nested)
■ Interfaces
■ Method local inner classes
■ Inner class methods and instance variables
■ Local variables