Programming and Problem Solving with Java

CASE STUDY

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takes the values as arguments and stores the values into its fields. Have we forgotten

anything else? The entry is to be written to a file. Should the Entry class be responsible

for writing itself to a file or should the driver provide this function? Encapsulation dic-

tates that the Entry should bear this responsibility. Here, then, is our revised CRC card

for Entry:

The knowledge responsibilities give us at least a partial list of the instance variables

of the Entryclass: a Name, an Address, and a Phone. There may be other internal fields. If

so, we can add them later. We have a Nameclass and a Phoneclass. The only classes left to

write are Address,Entry, and a driver.

In Chapter 7, we will examine several different versions of addresses. For this appli-

cation, let’s just use the street, city, state, and ZIP code. We should have one constructor

that takes these attributes as parameters. Let’s include another constructor that reads

values into its fields. There should be four knowledge responsibilities, one for each of

these fields. The first three fields should be strings. What about the ZIP code? If the ZIP

code is just the standard five digits, we could use an integer. However, many ZIP codes

now use five digits, plus a hyphen and four more digits. To cover both cases, let’s use a

string to represent the ZIP code. Should this class provide the values in these fields in a

variety of formats like the Nameclass does? Not at this stage. We are only creating the

address book now, not processing the information in some way.

Class Name: Entry Superclass: Subclasses:

Responsibilities Collaborations

Create (name, address, phone) Name, Address, Phone

Create( ) Name, Address, Phone, BufferedReader

Know name None

return Name

Know address None

return Address

Know phone number None

return Phone

Write entry to a file (outfile) PrintWriter