一个有用的ANSI字符串类String的实现及使用演示

来源：互联网发布：雅思备考资料知乎编辑：程序博客网时间：2024/06/05 22:41

和C#不一样，C和C++的内部都没有字符串数据类型，但是我们可以用C++建立一个实现字符串相关操作的类型：String

并且利用重载的机制提供方便操作字符串的相关运算符集。

下面的程序分成两个部分：

（1）String类：类头String.h和类实现String.cpp

（2）String类使用演示程序Main.cpp

类头文件String.h代码如下：

#ifndef STRING_H 
#define STRING_H 
#include <iostream> 
using namespace std; 
class String 
{ 
    friend ostream & operator<<(ostream & output, const String & s); 
    friend istream & operator>>(istream & input, String & s); 
public: 
    String(const char* = ""); 
    String(const String &); 
    ~String(); 
    const String & operator=(const String &);   //赋值 
    String & operator+=(const String &);        //字符串连接 
    int operator!() const;                      //String为空？ 
    int operator==(const String &) const;       //测试s1==s2 
    int operator!=(const String &) const;       //测试s1!=s2 
    int operator<(const String &) const;        //测试s1<s2 
    int operator>(const String &) const;        //测试s1>s2 
    int operator<=(const String &) const;       //测试s1<=s2 
    int operator>=(const String &) const;       //测试s1>=s2 
    char & operator[](int);                     //返回对字符的引用 
    String & operator()(int, int);              //返回一个子字符串 
    int GetLength() const;                      //返回字符串的长度，不包括结尾的/0 
private: 
    char* sPtr;                                 //指向字符串起始位置的指针 
    int length;                                 //字符串的长度 
}; 
#endif

类实现文件String.cpp代码如下：

#include <iostream> 
#include <string.h> 
#include <assert.h> 
#include "String.h" 
ostream & operator<<(ostream & output, const String & s) 
{ 
    output<<s.sPtr; 
    return output; 
} 
istream & operator>>(istream & input, String & s) 
{ 
    static char temp[100]; 
    input>>temp; 
    s = temp; 
    return input; 
} 
String::String(const char * s) 
{ 
    cout<<"Convention constructor:"<<s<<endl; 
    length = strlen(s); 
    sPtr = new char[length+1]; 
    assert(sPtr!=0); 
    strcpy(sPtr, s); 
} 
String::String(const String & copy) 
{ 
    cout<<"Copy constructor:"<<copy.sPtr<<endl; 
    length = copy.length; 
    sPtr = new char[length+1]; 
    assert(sPtr != 0); 
    strcpy(sPtr, copy.sPtr); 
} 
String::~String() 
{ 
    cout<<"Destructor:"<<sPtr<<endl; 
    delete[] sPtr; 
} 
const String & String::operator=(const String & right) 
{ 
    cout<<"operator = called"<<endl; 
    if(&right != this)   //避免自我赋值 
    { 
        delete[] sPtr; 
        length = right.length; 
        sPtr = new char[length+1]; 
        assert(sPtr!=0); 
        strcpy(sPtr, right.sPtr); 
    } 
    else 
    { 
        cout<<"Attempt assignment of a String to itself/n"; 
    } 
    return *this; 
} 
String & String::operator+=(const String & right) 
{ 
    char* tempPtr = sPtr; 
    length += right.length; 
    sPtr = new char[length+1]; 
    assert(sPtr!=0); 
    strcpy(sPtr, tempPtr); 
    strcat(sPtr, right.sPtr); 
    delete[] tempPtr; 
    return *this; 
} 
//字符串为空？ 
int String::operator !() const 
{ 
    return length == 0; 
} 
int String::operator==(const String & right) const 
{ 
    return strcmp(sPtr, right.sPtr)==0; 
} 
int String::operator!=(const String & right) const 
{ 
    return strcmp(sPtr, right.sPtr)!=0; 
} 
int String::operator<(const String & right) const 
{ 
    return strcmp(sPtr, right.sPtr)<0; 
} 
int String::operator>(const String & right) const 
{ 
    return strcmp(sPtr, right.sPtr)>0; 
} 
int String::operator<=(const String & right) const 
{ 
    return strcmp(sPtr, right.sPtr)<=0; 
} 
int String::operator>=(const String & right) const 
{ 
    return strcmp(sPtr, right.sPtr)>=0; 
} 
//返回对String中某个字符的引用 
char & String::operator [](int subscript) 
{ 
    //首先测试下标是否越界 
    assert(subscript>=0 && subscript<length); 
    return sPtr[subscript]; 
} 
String & String::operator()(int index, int sublength) 
{ 
    //首先测试下标是否越界 
    assert(index>=0 && index<length && sublength >= 0); 
    String * subPtr = new String; 
    assert(subPtr!=0); 
    //计算子字符串长度 
    int size = 0; 
    if(sublength == 0 || (index+sublength>length)) 
    { 
        size = length - index + 1; 
    } 
    else 
    { 
        size = sublength + 1; 
    } 
    //分配子字符串内存 
    delete subPtr->sPtr; 
    subPtr->length = size; 
    subPtr->sPtr = new char[size]; 
    assert(subPtr->sPtr!=0); 
    int i = index, j=0; 
    //把子字符串拷贝到新的对象中 
    for( ; i<index+size-1; i++, j++) 
    { 
        subPtr->sPtr[j] = sPtr[i]; 
    } 
    subPtr->sPtr[j] = '/0'; 
    return *subPtr; 
} 
int String::GetLength() const 
{ 
    return length; 
}

String类使用演示程序Main.cpp代码如下：

#include <iostream> 
#include "String.h" 
int main() 
{ 
    cout<<"---------------------------------------------------------------------------------------------------------/n";  
    cout<<"                   一个有用的ANSI字符串类String的实现及使用演示程序                    /n";  
    cout<<"by 一剑(Loomman),QQ:28077188,MSN: Loomman@hotmail.com QQ裙：30515563/n";  
    cout<<"---------------------------------------------------------------------------------------------------------/n/n";  
    String s1(" happy"), s2(" birthday"), s3; 
    cout<<"s1 is /""<<s1<<"/"; s2 is /""<<s2 
        <<"/"; s3 is empty /n" 
        <<"The results of comparing s2 and s1:" 
        <<"/ns2==s1 yields "<<(s2==s1) 
        <<"/ns2!=s1 yields "<<(s2!=s1) 
        <<"/ns2>s1 yields "<<(s2>s1) 
        <<"/ns2<s1 yields "<<(s2<s1) 
        <<"/ns2>=s1 yields "<<(s2>=s1) 
        <<"/ns2<=s1 yields "<<(s2<=s1)<<"/n/n"; 
    cout<<"Testing! s3:/n"; 
    if(!s3) 
    { 
        cout<<"s3 is empty; assigning s1 to s3; /n"; 
        s3 = s1; 
        cout<<"s3 is /""<<s3<<"/"/n/n"; 
    } 
    cout<<"s1+=s2 yields s1="; 
    s1+=s2; 
    cout<<s1<<"/n/n"; 
    cout<<"s1+=/" to you/" yields/n"; 
    s1+=" to you"; 
    cout<<"s1="<<s1<<"/n/n"; 
    cout<<"The substring of s1 starting at /n" 
        <<"location 0 for 14 characters, s1(0, 14), is:" 
        <<s1(0, 14)<<"/n/n"; 
    cout<<"The substring of s1 starting at /n" 
        <<"location 15, s1(15, 0) is:" 
        <<s1(15, 0)<<"/n/n"; 
    String * s4Ptr = new String(s1); 
    cout<<"*s4Ptr="<<*s4Ptr<<"/n/n"; 
    cout<<"assigning *s4Ptr to *s4Ptr/n"; 
    *s4Ptr = *s4Ptr; 
    cout<<"*s4Ptr="<<*s4Ptr<<endl; 
    delete s4Ptr; 
    s1[0] = 'H'; 
    s1[6] = 'B'; 
    int a; 
    cin>>a; 
    return a; 
}

程序运行效果：

----------------------------------------------------------------------------------------------------------
      一个有用的ANSI字符串类String的实现及使用演示程序
      by 一剑(Loomman),QQ:28077188,MSN: Loomman@hotmail.com QQ裙：30515563
      ----------------------------------------------------------------------------------------------------------

Convention constructor: happy
Convention constructor: birthday
Convention constructor:
s1 is " happy"; s2 is " birthday"; s3 is empty
The results of comparing s2 and s1:
s2==s1 yields 0
s2!=s1 yields 1
s2>s1 yields 0
s2<s1 yields 1
s2>=s1 yields 0
s2<=s1 yields 1

Testing! s3:
s3 is empty; assigning s1 to s3;
operator = called
s3 is " happy"

s1+=s2 yields s1= happy birthday

s1+=" to you" yields
Convention constructor: to you
Destructor: to you
s1= happy birthday to you

Convention constructor:
The substring of s1 starting at
location 0 for 14 characters, s1(0, 14), is: happy birthda

Convention constructor:
The substring of s1 starting at
location 15, s1(15, 0) is: to you

Copy constructor: happy birthday to you
*s4Ptr= happy birthday to you

assigning *s4Ptr to *s4Ptr
operator = called
Attempt assignment of a String to itself
*s4Ptr= happy birthday to you
Destructor: happy birthday to you