简单字符串类实现

[转 http://www.dogame.com.cn/gamerc/jc_show.php?id=6051】

main函数：
#include <iostream>
#include "strings.h"
using namespace std;
int main(){
Strings s3;
Strings s4;
Strings s5;
s3.display();
Strings s1("hello");
s1.display();
Strings s2(s1);
s2.display();
s3 = s2;
s3.display();
s4 = s1+s2;
s4.display();
s5 = s4 + "good";
s5.display();
return 0;
}

strings.h函数
#ifndef _STRINGS_
#define _STRINGS_
#include<iostream>
using namespace std;
class Strings{
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;
}
display();
private:
char *str;
};
#endif

strings.cpp函数
#include "strings.h"
#include <iostream>
using namespace std;
Strings::Strings(){ // 默认构造函数
str = new char('A'); //初试化为字符A
//str = "nothing"; 试试如此初试话 :-) 呵呵
cout<<"Strings is called"<<endl;
}
Strings::Strings(char *s){
str = new char[strlen(s) + 1]; // 带一个参数的构造函数
if(str)
strcpy(str, s);
cout<<"Strings(char *s) is called"<<endl;
}
Strings::Strings(const Strings &s){ // copy构造函数
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){ // 赋值运算
if(this != &s){ // 如果str不是它本身
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){ // 加法运算
char * temp;
 temp = new char[strlen(str)+strlen(s.str)+1]; //需要重新申请内存，原来的内存不够
strcpy(temp, str);
delete [] str;
strcat(temp,s.str);
str = temp;
return *this;
}
Strings& Strings::operator + (const char *s){ // 加法运算
char * temp;
temp = new char[strlen(str)+strlen(s)+1];
strcpy(temp, str);
delete [] str;
strcat(temp,s);
str = temp;
return *this;
}
Strings::display(){ // 显示函数
char *p=str;
while(*p != '\0'){
cout<<*p;
p ++;
}
cout<<endl;
cout<<"display is called "<<endl;
}