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STRINGS, THE STRING CLASS, AND THE STRINGBUILDER CLASS in .NET Access PDF417 in .NET STRINGS, THE STRING CLASS, AND THE STRINGBUILDER CLASS




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STRINGS, THE STRING CLASS, AND THE STRINGBUILDER CLASS generate, create none none on none projects Jasper Reports stBuff.AppendFormat none for none (Constants.vbCrLf & _ "We have {0000} widgets left.

", 12) Console.WriteLine(stBuff) Console.Read() End Sub End Module.

The output from thi s program looks like this:. The format speci ca none none tion is enclosed within curly braces that are embedded in a string literal. The data after the comma are placed into the speci cation when the code is executed. See the VB.

NET documentation for a complete list of format speci cations. Next we consider the Insert method. This method allows us to insert a string into the current StringBuilder object.

The method can take up to three arguments. The rst argument speci es the position to begin the insertion. The second argument is the string you want to insert.

The third argument, which is optional, is an integer that speci es the number of times you want to insert the string into the object. Here s a small program that demonstrates how to use the Insert method:. Imports System.text Module Module1 Sub Main() Dim stBuff As New StringBuilder stBuff.Insert(0, "Hello") stBuff.

Append("world") stBuff.Insert(5, ", ") Console.WriteLine(stBuff) Dim chars() As Char = {"t"c, "h"c, "e"c, "r"c, "e"} stBuff.

Insert(5, " " & chars) Console.WriteLine(stBuff). The StringBuilder Class Console.Read() End Sub End Module The output is Hello, world Hello there, world The following progr none for none am utilizes the Insert method using the third argument for specifying the number of insertions to make:. Dim stBuff As New S tringBuilder stBuff.Insert(0, "and on ", 6) Console.WriteLine(stBuff).

Here s the output:. and on and on and on and on and on and on The StringBuilder c none for none lass has a Remove method for removing characters from a StringBuilder object. This method takes two arguments: a starting position and the number of characters to remove. Here s how it works:.

Dim stBuff As New S tringBuilder("noise in +++++string") stBuff.Remove(9, 5) Console.WriteLine(stBuff).

The program outputs noise in string You can replace cha none for none racters in a StringBuilder object with the Replace method. This method takes two arguments: the old string to replace and the new string to put in its place. The following code fragment demonstrates how the method works:.

Dim stBuff As New S tringBuilder("recieve decieve reciept") stBuff.Replace("cie", "cei") Console.WriteLine(stBuff).

Each cie is replaced with cei . STRINGS, THE STRING CLASS, AND THE STRINGBUILDER CLASS When working with S none none tringBuilder objects, you will often want to convert them to strings, perhaps to use a method that isn t found in the StringBuilder class. You can do this with the ToString method. This methods returns a String instance of the current StringBuilder instance.

Here s an example:. Imports System.text Module Module1 Sub Main() Dim stBuff As New StringBuilder("HELLO WORLD") Dim st As String = stBuff.ToString() st = st.

ToLower() st = st.Replace(st.Substring(0, 1), _ st.

Substring(0, 1). ToUpper()) stBuff.Replace(stBuff.

ToString, st) Console.WriteLine(stBuff) Console.Read() End Sub End Module.

This program displa none for none ys the string, Hello world by rst converting stBuff to a string (the st variable), making all the characters in the string lowercase, capitalizing the rst letter in the string, and then replacing the old string in the StringBuilder object with the value of st. The ToString method is used in the rst argument of Replace because the rst parameter is supposed to be a string. You can t call the StringBuilder object directly here.

. COMPARING THE EFFICIENCY OF THE AND STRINGBUILDER CLASSES STRING We end this chapter with a discussion of how the String class and the StringBuilder class compare in ef ciency. We know that String objects are immutable and StringBuilder objects are not. It is reasonable to believe, then, that the StringBuilder class is more ef cient.

However, we don t want to always use the StringBuilder class because the StringBuilder class lacks several methods we need to perform reasonably powerful string processing. It is true that we can transform StringBuilder objects into String objects (and then back again). Comparing the Ef ciency of the String and StringBuilder Classes when we need to use String methods (see the previous section), but we must know when we need to use StringBuilder objects and when we can get by with just String objects. The test we use is very simple. Our program has two subroutines one that builds a String object of a speci ed size and another that builds a StringBuilder object of the same size.

Each of the subroutines is timed, using objects from the Timing class we developed at the beginning of the book. This procedure is repeated three times, rst for building objects of 100 characters, then for 1,000 characters, and nally for 10,000 characters. The times are then listed in pairs for each size.

Here s the code we used:. Option Strict On Im none none ports Timing Imports System.text Module Module1 Sub Main() Dim size As Integer = 100 Dim timeSB As New Timing Dim timeST As New Timing Dim index As Integer Console.WriteLine() For index = 1 To 3 timeSB.

startTime() BuildSB(size) timeSB.stopTime() timeST.startTime() BuildString(size) timeST.

stopTime() Console.WriteLine _ ("Time (in milliseconds) to build StringBuilder " & _ "object for " & size & " elements: " & _ timeSB. Result.

TotalMilliseconds) Console.WriteLine _ ("Time (in milliseconds) to build String object " & _ "for " & size & " elements: " & timeST.Result.

_ TotalMilliseconds).
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