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VB2008从入门到精通(PDF格式英文版)-第51部分
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even slightly； you must instantiate a new object； which would be the case if we used the = and
± operators。 The StringBuilder type is like String； except the referenced text can be modified。
In the Process（） implementation； the Do While loop calls the method Peek（）； which reads；
but does not remove； a character value from the stream。 If there is nothing more to read； a …1
value is returned。 Otherwise； data is available； and the method ReadLine（） can be called。
ReadLine（） will read a buffer of characters until a newline or return character is encountered。
Having read a line of text； it is split into the individual fields using the Split（） method。 The split
characters are the space and tab character （ControlChars。Tab）。
When the Split（） method returns； the individual fields are assigned to the array splitUpText。
Those array elements are iterated and appended to the StringBuilder variable retval； but each
element is surrounded by a set of brackets。 The brackets provide a set of boundaries that you
can inspect to see what data has been found。 I include the brackets purely for debugging purposes。
Because I am trying to reformat the stream； I append a newline character （ControlChars。NewLine） to
the variable retval。
When all of the lines of text and fields within the lines of text are iterated； a string represen
tation of the StringBuilder instance is returned using the ToString（） method。 Running the
code shows how many fields each line of text has and how you should format the text file。 This
gives you an understanding of how the file is structured。
The following is sample output from the lotto。txt file。
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CH A PT E R 1 0 ■ L E A R N I N G A B O U T P E R S IS T E N CE 265
（2000。01。15）（6）（10）（25）（26）（38）（42）（20）
（2000。01。19）（2）（16）（18）（23）（32）（43）（26）
（2000。01。22）（4）（5）（6）（24）（34）（38）（9）
（2000。01。26）（3）（20）（22）（24）（34）（39）（9）
（2000。01。29）（7）（12）（13）（34）（38）（39）（28）
（2000。02。02）（1）（18）（22）（28）（35）（43）（32）
（2000。02。05）（4）（13）（15）（31）（32）（45）（37）
（2000。02。09）（1）（29）（31）（34）（39）（41）（25）
。。。
（2006…12…27）（11）（13）（17）（21）（24）（26）（38）（578199）（735993）（）（）
（2006…12…30）（3）（13）（22）（30）（35）（41）（34）（142968）（472679）（）
（）
（）
（）
（2007…01…03）（5）（24）（37）（39）（41）（44）（9）（049802）（133875）（）（）
（2007…01…06）（3）（7）（23）（27）（30）（32）（38）（687442）（874814）（）（）
（2007…01…10）（7）（9）（13）（23）（35）（37）（25）（039498）（648301）（）（）
（2007…01…13）（3）（17）（22）（37）（39）（43）（34）（968842）（162860）（）（）
（2007…01…17）（12）（16）（27）（33）（37）（41）（24）（663824）（765917）（）（）
The sample output shows that we have the following items to fix：
o There are empty lines of text where no data has been defined。
o Some lines of text have empty fields at the end。
o Some fields have an incorrect date format。
o Some dates have duplicates； which need to be removed。
o Some lines of text have too many fields。 We need to figure out which fields we want to
keep and which we can discard。
■Note When processing streams and cleaning them up； it is important to take the stream apart first and
see what you are up against。 Do not make assumptions until you have looked at the individual pieces of data。
Then you will be able to determine the steps you need to undertake to fix the stream。
Fixing the Stream
The final solution uses the same code used to parse the lines of text and individual fields； as
follows （note； however； that we need the individual lines if the date format is correct； so we
store each one in the lineOfText variable）：
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266 CH AP T E R 1 0 ■ L E A R N I N G A B OU T P E R S IS TE N CE
Public Class LottoTicketProcessor ： Implements IProcessor
Private _dates As IList（Of String） = New List（Of String）（）
。 。 。
Public Function Process（ByVal input As String） As String
Implements IProcessor。Process
Dim reader As TextReader = New StringReader（input）
Dim retval As StringBuilder = New StringBuilder（）
Do While reader。Peek（） …1
Dim lineOfText As String = reader。ReadLine（）
Dim splitUpText As String（） =
lineOfText。Split（New Char（） ｛〃 〃c； ControlChars。Tab｝）
If _dates。Contains（splitUpText（0）） Then
Continue Do
End If
If splitUpText（0）。Length = 0 Then
Continue Do
End If
If splitUpText（0）。Contains（〃…〃） Then
Dim dateSplit As String（） = splitUpText（0）。Split（New Char（） ｛〃…〃c｝）
Dim newDate As String =
dateSplit（0） & 〃。〃 & dateSplit（1） & 〃。〃 & dateSplit（2）
If _dates。Contains（newDate） Then
Continue Do
End If
_dates。Add（newDate）
retval。Append（newDate）
For c1 As Integer = 0 To 7
retval。Append（〃 〃 & splitUpText（c1））
Next
Else
_dates。Add（splitUpText（0））
retval。Append（lineOfText）
End If
retval。Append（ControlChars。NewLine）
Loop
Return retval。ToString（）
End Function
。 。 。
End Class
■Note In the downloadable source code； the individual steps taken to clean up the data stream are demon
strated。 For reference； the intermediate development steps in the source code are called Process01（）
through Process05（）。
Let’s review how this code fixes the five problems we discovered。
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Empty Lines of Text
The following code removes the empty lines of text。
If splitUpText（0）。Length = 0 Then
Continue Do
End If
When lotto。txt was processed； the output data stream generated a single field array for
an empty line。 So； we know that if the first field element has a length of zero； the line of text
should be ignored。
Empty Fields and Too Many Fields
The next problem in our list is that some lines have empty text fields at the end。 Solving this
problem would probably entail a solution similar to the previous one； but you should think of
the big picture and understand that solving one problem might also solve another problem。 In
this case； solving the problem of the empty fields also helps solve the problem of having too
many fields。
Both of these problems are solved by knowing the data that is being manipulated。 As you’ve
seen； the data stream assumes the following format： date； then lottery numbers 1 to 6； and then
the bonus number。 The parts of the data stream that are not correct have the same format； with
some extra information like replay number and empty fields。 Thus； the fix is to copy the date
and append the remaining fields； as follows：
retval。Append（newDate）
For c1 As Integer = 0 To 7
retval。Append（〃 〃 & splitUpText（c1））
Next
The first line of code appends the date to the StringBuilder buffer （retval）。 Then in the
For loop that follows； a space and the fields 0 to 7 are copied to the StringBuilder buffer。
Incorrect Data Format
In some of the fields； the date has a period separator； in others； it has a hyphen。 The correct
format is a period； and the code that fixes the date format is as follows：
If splitUpText（0）。Contains（〃…〃） Then
Dim dateSplit As String（） = splitUpText（0）。Split（New Char（） ｛〃…〃c｝）
Dim newDate As String =
dateSplit（0） & 〃。〃 & dateSplit（1） & 〃。〃 & dateSplit（2）
A fix is needed if the first field contains a hyphen。 The If statement tests for this using the
Contains（） method。 If a fix is needed； the first field is separated again into three subfields； where
each subfield represents a part of the date （year； month； day）。 Then those three subfields are
rebined and separated using the period and assigned to the variable newDate。
Duplicate Dates
The last problem that needs to be solved is having duplicate dates in the data stream。 The
following code fixes this problem （the duplicate date code is bolded）。
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268 CH AP T E R 1 0 ■ L E A R N I N G A B OU T P E R S IS TE N CE
If _dates。Contains（splitUpText（0）） Then
Continue Do
End If
If splitUpText（0）。Length = 0 Then
Continue Do
End If
If splitUpText（0）。Contains（〃…〃） Then
Dim dateSplit As String（） = splitUpText（0）。Split（New Char（） ｛〃…〃c｝）
Dim newDate As String = _
dateSplit（0） & 〃。〃 & dateSplit（1） & 〃。〃 & dateSplit（2）
If _dates。Contains（newDate） Then
Continue Do
End If
_dates。Add（newDate）
retval。Append（newDate）
For c1 As Integer = 0 To 7
retval。Append（〃 〃 & splitUpText（c1））
Next
Else
_dates。Add（splitUpText（0））
retval。Append（lineOfText）
End If
Of all the problems we needed to solve； this is the trickiest； because it required multiple
pieces of code in multiple places。 The code processes the data stream and keeps a list of dates。
A date is added to the list only if the date does not exist in the list； which is checked using the
Contains（） method。 The lists expose this method to verify if the object being passed to it
equals one of the list members。 The way that most lists implement the method is to iterate each
method and call the Equals（） method。 The catch is that if you declare a custom type； the Equals（）
method defaults to verifying if one reference value equals another。 You would need to imple
ment a custom Equals（） method。
■Note When you encounter situations where you need to write multiple pieces of code in multiple places；
that is a sign that you are about to create code that is hard to maintain。 You should take a close look at the
code； and If possible； rewrite it。 Of course； this depends on a lot of factors。 So sometimes； you will need to
just write the code； test it； and hope that it works。
With the final solution； the console application TextProcessor is plete。 You could
process lotto。txt and get a correctly formatted data stream。
Piping Binary Data
When working with the console； for the most part； you will be transferring text data from one
process to another or from one file to another file。 However； when developing in ； working
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with text is not always the best choice。 A more efficient approach might be to store the data in
a binary format。
The easiest way to understand the difference between text data and binary data is to open
a binary file using a text editor； as shown in Figure 10…8。
Figure 10…8。 A binary file in a text editor
In Figure 10…8； you see just a bunch of funny characters with some text scattered throughout。
A binary file is different from a text file in that the format of a binary file is whatever the program
that reads and writes the binary data decides。 The advantage of using a binary file is that you
can create plex structures。 The disadvantage is that only the developer of the reader/writer
program knows what the file contains。
Binary files are not always smaller； but they are more efficient because you do not need to
parse and process the data。 For example； in the text…based lottery data stream reader； we needed
to parse every single line and then split the line of text into individual fields； which were then
parsed as integers and assigned to a variable。 Using a binary file； you only need to create a
binary type； and read or write that type。
In this section； we will continue with the example of the lottery…prediction application； but
this time； create it as a console application that converts a text data stream into a binary data
stream and then back to a text stream。 You’ll see how you can pipe the data from one stream to
another by sending it from one application to another application。 When we are finished
building this application； the following mand line will be valid。
type lotto。txt ｜ TextProcessor。exe ｜ Text2Binary。exe ｜ Binary2Text。exe
The mand line starts with generating a text data stream using the type mand。
The mand TextProcessor。exe generates a clean data stream that is then piped into
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270 CH AP T E R 1 0 ■ L E A R N I N G A B OU T P E R S IS TE N CE
Text2Binary。exe； which generates a binary data stream。 Finally； the binary data stream is
converted back into a text stream using Binary2Text。exe； which displays the data on the console。
The architecture of TextProcessor with its implementation of the IProcessor interface
and a general architecture of grabbing a file or console input/output stream worked。 However；
IProcessor is not usa
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