自己写一个string类

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头文件：

#ifndef _STRINGS_#define _STRINGS_#include <iostream>using namespace std;class Strings{friend ostream& operator<<(ostream& os, const Strings& s);public:Strings();Strings(char *s);Strings(const Strings &s);Strings& operator = (const Strings& s);Strings& operator + (const Strings& s);Strings& operator + (const char *s);~Strings(){if(str != NULL)delete [] str;cout<<"~Strings() is called"<<endl;}void display();private:char *str;};#endif

源文件：

#include "strings.h"#include <cstring>#include <iostream>using namespace std;ostream& operator<<(ostream& os, const Strings& s){cout<<s.str;return os;}Strings::Strings(){str = new char('A');cout<<"Strings (char *s) is called"<<endl;}Strings::Strings(char *s){str = new char[strlen(s)+1];if (str){strcpy(str, s);}cout<<"Strings(char *s) is called"<<endl;}Strings::Strings(const Strings &s){str = new char[strlen(s.str)+1];if(str){strcpy(str, s.str);}cout<<"Strings(const Strings &s) is called"<<endl;}Strings& Strings::operator =(const Strings &s){if(this != &s){if (str != NULL){delete [] str;    //防止内存泄露}str = new char[strlen(s.str)+1];strcpy(str, s.str);cout<<"Strings(const Strings &s) is called"<<endl;}return *this;}Strings& Strings::operator +(const Strings& s){char *temp;temp = new char[strlen(str)+strlen(s.str)+1];strcpy(temp, str);delete [] str;strcat(temp, s.str);str = temp;return *this;}Strings& Strings::operator + (const char *s){char *temp;temp = new char[strlen(str)+strlen(s)+1];strcpy(temp, str);delete [] str;strcat(temp, s);str = temp;return *this;}void Strings::display() {char *p = str;while (*p != '\0'){cout<<*p;p++;}cout<<endl;cout<<"display is called"<<endl;}

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