Earlier in Lesson A9, Recursion, the concept of a stack was introduced. A stack is a linear data structure with well-defined insertion and deletion routines. Data is both placed and taken from the ‘top’ of the stack. Queues are very similar to stacks, except that Queues remove data from the front while adding data at the end.

The key topics for this lesson are:

1. Stacks
2. The Java Stack Class
3. Queues
4. The Java Queue Interface