• Methods for creating unmodifiable and synchronized views of attribute sets.
• operations useful for building implementations of interface AttributeSet

An unmodifiable view U of an AttributeSet S provides a client with "read-only" access to S. Query operations on U "read through" to S; thus, changes in S are reflected in U. However, any attempt to modify U, results in an UnmodifiableSetException. The unmodifiable view object U will be serializable if the attribute set object S is serializable.

A synchronized view V of an attribute set S provides a client with synchronized (multiple thread safe) access to S. Each operation of V is synchronized using V itself as the lock object and then merely invokes the corresponding operation of S. In order to guarantee mutually exclusive access, it is critical that all access to S is accomplished through V. The synchronized view object V will be serializable if the attribute set object S is serializable.

As mentioned in the package description of javax.print, a null reference parameter to methods is incorrect unless explicitly documented on the method as having a meaningful interpretation. Usage to the contrary is incorrect coding and may result in a run time exception either immediately or at some later time. IllegalArgumentException and NullPointerException are examples of typical and acceptable run time exceptions for such cases.