#include<iostream>
#include<cstring>
#include<cassert>
#include<iomanip>

using namespace std;
class String;
istream& operator>>(istream&, String&);
ostream& operator<<(ostream&,const String&);

class String
{
public:
?//構(gòu)造函數(shù)
?//String s1();
?//String s1("abc");
?//String s2(s1);
?String();
?String(const char*);
?String(const String&);
?//析構(gòu)函數(shù)
?~String();
?//賦值操作
?String& operator=(const char*);
?String& operator=(const String&);
?//等于操作
?bool operator==(const char*);
?bool operator==(const String&);
?//加操作
?String operator+(const String&) const;
?//下標(biāo)操作
?char& operator[](int);
?//成員操作
?int size(){return _size;}
?char* c_str(){return _string;}
?//記數(shù)操作
?int count(const char) const;
private:
?int? _size;
?char *_string;
};

inline String::String()??????????????????????????????????? //構(gòu)造函數(shù)
{
?_size=0;
?_string=0;
}

inline String::String(const char* str)???????????????????? //構(gòu)造函數(shù)
{
?if(!str)
?{
??_size=0;
??_string=0;
?}
?else
?{
??_size=strlen(str);
??_string=new char[_size+1];
??strcpy(_string,str);
?}
}

inline String::String(const String& str)????????????????? //拷貝構(gòu)造函數(shù)
{
?if(!str._size)
?{
??_size=0;
??_string=0;
?}
?else
?{
??_size=strlen(str._string);
??_string=new char[_size+1];
??strcpy(_string,str._string);
?}
}

inline String::~String()????????????????????????????????? //析構(gòu)函數(shù)
{
?delete[] _string;
}

inline String& String::operator=(const char* str)???????? //賦值操作
{
?if(!str)
?{
??_size=0;
??delete[] _string;
??_string=0;
?}
?else
?{
??_size=strlen(str);
??delete[] _string;
??_string=new char[_size+1];
??strcpy(_string,str);
?}
?return *this;
}

inline String& String::operator=(const String &str)????? //賦值操作
{
?if(this!=&str)
?{
??_size=str._size;
??delete[] _string;
??_string=new char[_size+1];
??strcpy(_string,str._string);
?}
?return *this;
}

inline bool String::operator==(const String &rhs)????????? //等于操作符重載
{
?if(_size!=rhs._size)
??return false;
?return strcmp(_string,rhs._string)?false:true;
}

inline bool String::operator==(const char *str)??????????? //等于操作符重載
{
?return strcmp(_string,str)?false:true;
}

inline char& String::operator[](int n)???????????????????? //下標(biāo)訪問符
{
?assert(n>=0 && n<_size);
?return _string[n];
}

inline int String::count(const char s) const?????????????? //記數(shù)操作
{
?int tempCount=0;
?for(int i=0;i<_size;i++)
?{
??? ?if(_string[i]==s)
???++tempCount;
?}
?return tempCount;
}

inline String String::operator+(const String& str) const? //加操作
{
?String tempStr;
?tempStr._size=_size+str._size;
?tempStr._string=new char[tempStr._size+1];
?strcpy(tempStr._string,_string);
?strcat(tempStr._string,str._string);
?return tempStr;
}

inline istream& operator>>(istream &io,String &str)?????? //輸入流
{
?const int limit_string_size =4096;
?char inBuf[limit_string_size];
?io>>setw(limit_string_size)>>inBuf;
?str=inBuf;
?return io;
}

inline ostream& operator<<(ostream &os,String &str)?????? //輸出流
{
?return os<<str.c_str();
}

int main()
{
?String str1="abc";
?String str2="def";
?str1.size();
?cout<<"size :"<<str1.size()<<endl;
?cout<<"b count :"<<str1.count('b')<<endl;
?String str3=str1+str2;
?cout<<str3;????? //該處不能為String&，只能為String。見String operator+()和ostream& operator<<(ostream &os,String &str)
?return 0;
}

SO GOOD!