自定义的精简版String类，重载了各种字符串的运算符操作

        最近几天温习了字符串的相关知识，比较了C语言的字符串操作以及C++的string类字符串的操作，个人觉得C++的string类字符串操作方便很多。至少不用太在意字符串的内存分配，而且它还有比较方便的字符串搜索、插入等方法，便于对字符串的各种操作。出于学习巩固知识的目的，自己写了一个精简版的String类，这个类只是重载了几种简单的字符串运算操作符，还没有写搜索、插入等方法。以后再慢慢完善！

        

//自定义版string类#include <iostream>using namespace std;class String {public:    String();//默认构造函数用于创建空字符串    ~String();//析构函数，如若创建临时变量时，会有很重要的意义    String(const String &rs);//拷贝构造函数    String(const char* const ch);//参数为数组字符串的构造函数    char &operator[](unsigned short int length);//下标操作符，由于不可能为负数，所以参数限定为ushort型    char operator[](unsigned short int length)const;//cons修饰函数体，一来作为下标操作函数的重载，二来为了针对const对象的操作    String &operator=(const String &s);//赋值运算符函数用于String对象之间的赋值String &operator=(const char* const ch);//常量字符串赋值运算函数    String operator+(const String &);//重载+运算符，实现String类对象的相加操作String operator+(const char* const ch);    void operator+=(const String &rs);//重载+=运算符，实现String类对象的相加并重新赋值操作void operator+=(const char* const ch);//重载<<操作符，由于<<为二元运算符，若写成String类的成员函数的话，它的参数只能有一个，所以，这里写成友元函数，这样就可以传入两个参数//cout<<s2等价于operator<<(cout,s2);    friend ostream &operator<<(ostream &o, const String &str)    {        o<<str.str;return o;    }    friend istream &operator>>(istream &i, String &str)    {        i>>str.str;        return i;    }    friend bool operator<(const String &str1, const String &str2)    {if(strcmp(str1.str, str2.str)<0)return 1;elsereturn 0;    }    friend bool operator>(const String &str1, const String &str2)    {if(strcmp(str1.str, str2.str)>0)return 1;elsereturn 0;    }    friend bool operator==(const String &str1, const String &str2)    {if(strcmp(str1.str, str2.str) == 0)return 1;elsereturn 0;    }    unsigned short int getlen()const{return len;}    const char*getstr()const{return str;}private:    String(unsigned short int);//不对外提供此构造函数的接口    unsigned short int len;    char *str;};String::String(unsigned short int length){cout<<"整型变量为参数的构造函数"<<endl;    str = new char[length + 1];    int i;    for(i=0; i<=length; i++){        str[i] = '\0';}    len = length;}String::String(){cout<<"默认构造函数"<<endl;    len = 0;    str = new char[1];    str[0] = '\0';}String::~String(){cout<<"String类析构函数"<<endl;    delete []str;    len = 0;}String::String(const String &rs){cout<<"拷贝构造函数"<<endl;    len = rs.getlen();    str = new char[len + 1];    for(int i=0; i<len; i++){        str[i] = rs[i];}    str[len] = '\0';}String::String(const char* const ch){cout<<"常量字符串为参数的构造函数"<<endl;    len = strlen(ch);    str = new char[len+1];    for(int i=0; i<len; i++)        str[i] = ch[i];    str[len] = '\0';}char &String::operator[](unsigned short int length){cout<<"String对象【】运算符"<<endl;    if(length>len)//限制数组越界操作        return str[len-1];    else        return str[length];}char String::operator[](unsigned short int length)const{cout<<"const String对象【】运算符"<<endl;    if (length>len)//限制数组越界操作    {        return str[len-1];    }    else        return str[length];}String &String::operator=(const String&s){cout<<"String对象=运算符"<<endl;    if (this == &s)        return *this;if(str)delete[]str;    len = s.getlen();    str = new char[len+1];    for(int i=0; i<len; i++)    {        str[i] = s[i];//这里是对String类对象进行下标操作，所以要在String类中重载下标操作符，注意这里还是const对象操作    }    str[len] = '\0';    return *this;}String &String::operator=(const char* const ch){cout<<"常量字符串=运算符"<<endl;if(str)delete []str;len = strlen(ch);str = new char[len + 1];for(int i=0; i<len; i++){str[i] = ch[i];}str[len] = '\0';return *this;}String String::operator+(const String &rs){cout<<"String对象+运算符"<<endl;    int total = len + rs.getlen();    String temp(total);    int i,j;    for( i=0; i<len; i++)        temp[i] = str[i];    for( j=0; j<rs.getlen(); j++,i++)        temp[i] = rs[j];    temp[total] = '\0';    return temp;//值传递，创建临时变量，temp对象析构掉}String String::operator+(const char* const ch){cout<<"常量字符串+运算符"<<endl;int total = len + strlen(ch);String temp(total);int i,j;for( i=0; i<len; i++)temp[i]=str[i];for( j=0; j<strlen(ch); j++,i++)temp[i] = ch[j];temp[total] = '\0';return temp;//值传递，创建临时变量，temp对象析构掉}void String::operator+=(const String &rs)//如果是String对象与常量字符串相加，这里会调用构造函数{cout<<"String对象+="<<endl;    int total = len + rs.getlen();    String temp(total);    int i,j;    for(i=0;i<len;i++){        temp[i] = str[i];}    for(j=0; j<rs.getlen(); j++,i++){temp[i] = rs[j];}    temp[total] = '\0';    *this = temp;}void String::operator+=(const char* const ch){cout<<"常量字符串+="<<endl;int total = len + strlen(ch);String temp(total);//这里需要调用以整型变量为参数的构造函数int i,j;for(i=0;i<len;i++){temp[i] = str[i];}for(j=0; j<strlen(ch); j++,i++){temp[i] = ch[j];}temp[total] = '\0';*this = temp;}int main(){String s1;    cout<<"s1的长度:"<<s1.getlen()<<endl;    char*temp="help me";    s1 = temp;//调用常量字符串赋值函数    cout<<"s1:"<<s1.getstr()<<"\t s1的长度:"<<s1.getlen()<<endl;    char ch[10];    strcpy(ch,"all right");    s1 += ch;    cout<<"ch:\t"<<ch<<endl;    cout<<"s1:\t"<<s1.getstr()<<endl;    cout<<"s1:"<<s1<<endl;    s1[2]='o';    cout<<"s1:"<<s1<<endl;    cout<<"s1[999]:"<<s1[999]<<endl;    String s2 = "mother";    String s3("Mother");    cout<<"s2:"<<s2<<"\t s3:"<<s3<<endl;    String s4 = s2+s3;//拷贝构造函数    cout<<"s2+s3="<<s4<<endl;String s5 = "I love ";String s6 = s5 + "bupt";cout<<"s6:"<<s6<<endl;    int check = s2>s3;    cout<<"s2>s3:"<<check<<endl;    check = s2<s3;    cout<<"s2<s3:"<<check<<endl;    check = s2 == s2;    cout<<"s2==s2:"<<check<<endl;    cin>>s2[0]>>s3[0];    s2 = s2 + s3;    cout<<"s2:"<<"\t"<<s2<<endl;system("pause");    return 0;}