About Question enthuware.ocpjp.v7.2.1585 :

[sir_Anduin@yahoo.de]

It allows null value to be stored.

how does that work?

[admin]

Code: Select all

    HashSet hs = new HashSet();
    hs.add(null);
    System.out.println(hs);

Prints:

Code: Select all

[null]

HTH,
Paul.