Summary

Enhance several Subject$SecureSet methods to better deal with null values.

Problem

Subject$SecureSet is used to store principals and credentials returned by JAAS Subject's getPrincipals(), getPublicCredentials(), and getPrivateCredentials() methods. Since null is not allowed in this set, when contains(null) (and other methods) is called on such a set, an NPE is thown. This is slow comparing to returning null.

Solution

Switch from "throw-NPE" to "return false/ignore" when dealing with null values in multiple methods of Subject$SecureSet. Both styles are allowed by the Set interface.

Precisely,

1. when calling contains or remove on null, false is returned.
2. when calling containsAll on a collection containing null, false is returned
3. when calling removeAll, and retainAll on a collection containing a null value, the null value is ignored.

Specification

No spec change.