Queues

A Queue is a first-in-first-out collection of objects. An example of a queue is a line of waiting at a traffic light. The first car that arrived will be the first that leaves when the light turns green. New cars arriving are added to the end of the line. Then all cars will leave in the order they arrived.

I have created a class called ArrayQueue which implements a Queue. It has a contructor and three methods:

public ArrayQueue(int maxLength)

The constructor takes an argument that represents the maximum possible number of objects in the Queue.

public void insert(Object o)

Inserts a new object at the end of the Queue

public Object remove()

removes objects in the order they were inserted and returns the object removed

public int getLength()

Returns the number of objects in the Queue

Note the limitations of this array-based implementation of a Queue.

• Because the length of arrays cannot be increased after they are created, there is a limit to the number of objects we can add to the Queue. What happens if we try to add another object to a full Queue?
• There is currently no way to see what the first object (or any other object) in the Queue is without removing it. A getHead() method might be nice to do this.
• Another nice thing would be an isEmpty() method which returns true or false if we have removed all of the items from the Queue (or never added any). This way users of this class would be able to check to make sure they didn't attempt to remove objects from an empty Queue:

   do { /* process each object */ } until (  queue.isEmpty() );