11.CopyOnWriteArraySet

1. What it is. A copy-on-write set: ordered and without duplicates, implemented internally with CopyOnWriteArrayList. 2. How to use it. 3. Principle analysis. 3.1. Constructor. 3.1.1. The underlying implementation uses CopyOnWriteArrayList. 3.2. add method. 3.2.1. Delegates to CopyOnWriteArrayList.