string Constructors

Class string provides eight constructors for initializing strings in various ways. Figure 16.1 demonstrates the use of three of the constructors.

Figure 16.1. string constructors.

 1 // Fig. 16.1: StringConstructor.cs
 2 // Demonstrating string class constructors.
 3 using System;
 4
 5 class StringConstructor
 6 {
 7 public static void Main()
 8 {
 9 string originalString, string1, string2,
10 string3, string4;
11 char[] characterArray =
12 { 'b', 'i', 'r', 't', 'h', ' ', 'd', 'a', 'y' };
13
14 // string initialization 
15 originalString = "Welcome to C# programming!";
16 string1 = originalString; 
17 string2 = new string( characterArray ); 
18 string3 = new string( characterArray, 6, 3 ); 
19 string4 = new string( 'C', 5 ); 
20
21 Console.WriteLine( "string1 = " + """ + string1 + ""
" +
22 "string2 = " + """ + string2 + ""
" +
23 "string3 = " + """ + string3 + ""
" +
24 "string4 = " + """ + string4 + ""
" );
25 } // end method Main
26 } // end class StringConstructor
 
string1 = "Welcome to C# programming!"
string2 = "birth day"
string3 = "day"
string4 = "CCCCC"

Lines 910 declare the strings originalString, string1, string2, string3 and string4. Lines 1112 allocate the char array characterArray, which contains nine characters. Line 15 assigns string literal "Welcome to C# programming!" to string reference originalString. Line 16 sets string1 to reference the same string literal.

Line 17 assigns to string2 a new string, using the string constructor that takes a character array as an argument. The new string contains a copy of the characters in array characterArray.

Software Engineering Observation 16 1

In most cases, it is not necessary to make a copy of an existing string. All strings are immutabletheir character contents cannot be changed after they are created. Also, if there are one or more references to a string (or any object for that matter), the object cannot be reclaimed by the garbage collector.

Line 18 assigns to string3 a new string, using the string constructor that takes a char array and two int arguments. The second argument specifies the starting index position (the offset) from which characters in the array are to be copied. The third argument specifies the number of characters (the count) to be copied from the specified starting position in the array. The new string contains a copy of the specified characters in the array. If the specified offset or count indicates that the program should access an element outside the bounds of the character array, an ArgumentOutOfRangeException is thrown.

Line 19 assigns to string4 a new string, using the string constructor that takes as arguments a character and an int specifying the number of times to repeat that character in the string.

string Indexer, Length Property and CopyTo Method

Preface

Index

    Introduction to Computers, the Internet and Visual C#

    Introduction to the Visual C# 2005 Express Edition IDE

    Introduction to C# Applications

    Introduction to Classes and Objects

    Control Statements: Part 1

    Control Statements: Part 2

    Methods: A Deeper Look

    Arrays

    Classes and Objects: A Deeper Look

    Object-Oriented Programming: Inheritance

    Polymorphism, Interfaces & Operator Overloading

    Exception Handling

    Graphical User Interface Concepts: Part 1

    Graphical User Interface Concepts: Part 2

    Multithreading

    Strings, Characters and Regular Expressions

    Graphics and Multimedia

    Files and Streams

    Extensible Markup Language (XML)

    Database, SQL and ADO.NET

    ASP.NET 2.0, Web Forms and Web Controls

    Web Services

    Networking: Streams-Based Sockets and Datagrams

    Searching and Sorting

    Data Structures

    Generics

    Collections

    Appendix A. Operator Precedence Chart

    Appendix B. Number Systems

    Appendix C. Using the Visual Studio 2005 Debugger

    Appendix D. ASCII Character Set

    Appendix E. Unicode®

    Appendix F. Introduction to XHTML: Part 1

    Appendix G. Introduction to XHTML: Part 2

    Appendix H. HTML/XHTML Special Characters

    Appendix I. HTML/XHTML Colors

    Appendix J. ATM Case Study Code

    Appendix K. UML 2: Additional Diagram Types

    Appendix L. Simple Types

    Index



    Visual C# How to Program
    Visual C# 2005 How to Program (2nd Edition)
    ISBN: 0131525239
    EAN: 2147483647
    Year: 2004
    Pages: 600

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