Programming and Problem Solving with Java

(^526) | Array-Based Lists

CRC Card

Although we have designed our CRC card for a to-do list, the responsibilities outlined remain

valid for any kind of list. For example, if we are creating a list of people to invite to a wedding,

all of these operations are valid. We add names to the list, check whether a name is already

on the list, count the names on the list, check whether the list is full (that is, the length is equal

to the number of invitations bought), delete names, and review the names one at a time.

To make the rest of the discussion more concrete, let’s first assume that the items on the

list are strings. Later, we will see how the items can be made even more general.

Refining the Responsibilities

Let’s go back through the responsibilities, refining them, and converting them into method

headings. Because we are designing a general-purpose class, we do not have any specific sce-

narios that we can use. Instead, we will consider a variety of simplified scenarios that exemplify

how we believe the class may be employed. Because the class is intended for widespread use,

we should pay special attention to the documentation right from the design stage.

The observers, testing for full and empty, returning the number of items, and checking

whether an item is in the list, need no further discussion. Here are their method headings:

Class Name: List Superclass: Object Subclasses:

Responsibilities Collaborations

Create itself (maxItems) None

Is list full? None

return boolean

Is list empty? None

return boolean

Know length

Delete from list (item)

None

return int

None

Set up for iteration None

Know next item None

return boolean

Insert into list (item) None

Is an item in the list? None