Lecture 25 -- April 19, 2007

You need to get your major applications in or you will not be able to take your upper division CS classes although you will be able to register for them. You will be individually dropped from those classes unless you are an official CS major or minor.

We talked about stacks

as a last in first out (LIFO) data structure

as a data structure with two required operations: push and pop

with additional operations: isFull, isEmpty, peek

contiguous implementations : arrays of Objects

generic Vectors

type safe Vectors

linked implementations using Node as an external public class

using Node as an internal private class

We demonstrated that you can not remove the item at the bottom of the stack without removing the elements above it first.

We saw that the same test program worked identically regardless of the implementation of the Stack.

Each of the classes is named Stack in the code and must be renamed as such to be run with TestStack

ArrayStack.java - uses a generic array of Objects -

because it's an array, its size must be fixed at creation time

it currently has a default constructor with size 100

it could be augmented with an explicit value constructor if a different size were desired

GenericVectorStack.java - not type safe

TypeSafeStack.java - uses a Vector of Integers

LinkedListStack.java - has Node defined as an inner class

TestStack.java - puts 25 Integer elements on the stack, pops them off and prints them , then tries to pop a 26^th element off the stack and print it.

TestStack2.java - puts a variety of 8 Objects on the stack and then pops them off and prints them

Each of these classes is named Queue in the code

ArrayQueue.java

LinkedQueue.java

We talked about queues

as a first in first out (FIFO) data structure