C++--String类型各种重载函数的实现

来源：互联网发布：程序员常用的工具编辑：程序博客网时间：2024/06/05 23:07
#include <iostream>#include <string.h>#include <string>#include <stdio.h>using namespace std;class String{        friend bool operator == (const String &,const String &);        friend bool operator != (const String &,const String &);        friend bool operator <  (const String &,const String &);        friend bool operator >  (const String &,const String &);        friend bool operator <= (const String &,const String &);        friend bool operator >= (const String &,const String &);        friend ostream &operator <<(ostream &os,const String &s);        friend istream &operator >>(istream &os,String &s);public:        //无参构造函数        String()        {         pstr_=new char[1];        }        //有参构造函数        String (const char *s)        {         pstr_=new char[strlen(s)+1];         strcpy(pstr_,s);        }        //复制构造函数        String (const String &rhs)        {          pstr_=new char[strlen(rhs.pstr_)+1];          strcpy(pstr_,rhs.pstr_);        }        //赋值对象重载函数        String &operator = (const String &rhs)        {         if(this!=&rhs)//如果不是自复制         {          delete []pstr_;//先删除掉原有的内容          pstr_=new char[strlen(rhs.pstr_)+1];          strcpy(pstr_,rhs.pstr_);         }         return *this;        }        //赋值字符串重载函数        String &operator = (const char *s)        {         pstr_=new char[strlen(s)+1];         strcpy(pstr_,s);         return *this;        }        //重载+=运算符  左边对象本身发生了改变        String & operator +=(const String & rhs)        {         //用临时的字符串指针存放         char *tmp;         tmp=new char[strlen(pstr_)+strlen(rhs.pstr_)+1];         strcpy(tmp,pstr_);         strcat(tmp,rhs.pstr_);         delete []pstr_;         pstr_=tmp;         return *this;        }        String &operator += (const char *pstr)        {         char *tmp;         tmp = new char[strlen(pstr_)+strlen(pstr)+1];//先开空间         strcpy(tmp,pstr_);         strcat(tmp,pstr);         delete []pstr_;         pstr_=tmp;         return *this;        }        //重载[]下标运算符        char &operator[](size_t index)        {         static char sNULL='\0';         //要判断给出的下标越界的情况         if(index<strlen(pstr_) && index>0)         {          return pstr_[index];         }         else         {          cout<<"下标越界"<<endl;          return sNULL;         }        }        //重载const对象的运算符        const char &operator[](size_t index) const        {          static char sNULL='\0';         //要判断给出的下标越界的情况         if(index<strlen(pstr_) && index>0)         {          return pstr_[index];         }         else         {          cout<<"下标越界"<<endl;          return sNULL;         }        }        //返回字符串长度函数  函数后面加const代表这里面的所有变量只能读不能改        size_t size() const        {          return strlen(pstr_);        }        //重载c_str函数  返回的是当前字符串的首字符地址        const char* c_str()const        {         return pstr_;        }        //析构函数        ~String()        {         delete []pstr_;        }        //打印函数        void print()        {         if(pstr_==NULL)         {         cout<<""<<endl;         }        else        {         cout<<"string :"<<pstr_<<endl;        }        }private:        char *pstr_;};//重载== 函数bool operator == (const String &lhs,const String &rhs){        if(strcmp(lhs.pstr_,rhs.pstr_)==0)        {         return 1;        }        else         {         return 0;         }}//重载!=函数bool operator != (const String &lhs,const String &rhs){        if(strcmp(lhs.pstr_,rhs.pstr_)==0)        {         return 0;        }        else         {         return 1;         }}//重载< 函数bool operator <(const String &lhs,const String &rhs){        if(strcmp(lhs.pstr_,rhs.pstr_)<0)        {         return 1;        }        else        {         return 0;        }}//重载>函数bool operator >(const String &lhs,const String &rhs){        if(strcmp(lhs.pstr_,rhs.pstr_)>0)        {         return 1;        }        else        {         return 0;        }}//重载<=函数bool operator <=(const String &lhs,const String &rhs){        if(strcmp(lhs.pstr_,rhs.pstr_)<=0)        {         return 1;        }        else        {         return 0;        }}//重载>=函数bool operator >=(const String &lhs,const String &rhs){   if(strcmp(lhs.pstr_,rhs.pstr_)>=0)        {         return 1;        }        else        {         return 0;        }}//重载<<流ostream &operator <<(ostream &ofs,const String &rhs){        ofs<<rhs.pstr_<<endl;        return ofs;}//重载>>流istream &operator >>(istream &ifs, String &rhs){        char tmp[1024];//先开空间        ifs>>tmp;        rhs.pstr_=tmp;//输入的字符 放到rhs中        return ifs;}//重载+(两个对象之间)String operator +(const String &lhs,const String & rhs){        String str(lhs);        str+=rhs;        return str;}String operator +(const String &lhs,const char *s){        String str(lhs);        str+=s;        return str;}String operator +(const char *s,const String &rhs){        String str(rhs);        str+=s;        return s;}int main(){        String s1;//无参函数        s1.print();        String s2="hello";//有参函数        s2.print();        String s3=s2;//调用复制构造函数        s3.print();        String s4="world";//赋值对象重载函数        s4=s2;        s4.print();        String s5; //赋值字符串重载函数        s5="hello";        s5.print();        String s6="hello";//重载+=函数        String s7="world";        s6+=s7;        s6.print();        String s8="hello";//重载++函数        s8+="world";        s8.print();        s8[3]='A';        cout<<s8[3]<<endl;//重载[]运算符        s8.print();        String s9="hello";//重载c_str函数        const char* s;        s=s9.c_str();        cout<<s<<endl;        String s10="hello";        if(s9==s10)       //重载==        {         cout<<"equal"<<endl;        }        String s11="world";        if(s10!=s11)     //重载!=        {         cout<<"unequal"<<endl;        }        String s12="i am the max string";//重载<        if(s11<s12)        {         cout<<"右边字符串大"<<endl;        }        else        {        cout<<"左边字符串大"<<endl;        }       String s13="hello";//重载<<        cout<<s13;        String s14;//重载>>        cin>>s14;        cout<<s14;        String s15="hello";//重载+ 用到了+=        String s16="world";        cout<<s15+s16<<endl;        return 0;}
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