MutableBuffer Class,

File Class,

Date-, time-, and timing-related classes DateTime, TimeSpan, Alarm, Ticker, and the notification classes AlarmNotification and MessageNotification,

the synchronization classes EventSempahore and MutexSempahore,

Comparable class and Orderable class,

eight Comparator classes used for sorting (Caseless)Comparator, (Caseless)ColumnComparator, (Caseless)DescendingComparator, InvertingComparator, and NumericComparator, and

other miscellaneous classes Buffer, Monitor, Pointer, RegularExpression, RexxContext, RexxInfo, RexxQueue, StackFrame, StreamSupplier, Supplier, TraceObject, Validate, VariableReference, and WeakReference.