Contains

- ToDoManager.java: the final client code for the data structures, written
  using Java interfaces and an iterator
- Sequence.java: the interface for list data structures
- SinglyLinkedList.java: a class that implements the Sequence interface
- DoublyLinkedList.java: another class that implements the Sequence interface
- VectorSequence1.java: a third class that implements the Sequence interface
  (only works in Java 1.1 not 1.2); defined as a subclass of Vector
- VectorSequence2.java: a fourth class that implements the Sequence interface;
  defined by association with a Vector (the adapter design pattern)
- Queue.java: another example interface
- SequenceQueue.java: one very general queue implementation, using association
