String类

#include <iostream>
#include <string.h>

/* String 类 */
class String{
    char* str;
public:
    String();
    String(const char* s);
    String(String&s);
    ~String();
    const char* getStr() const;
    String& operator = (const char* s);
    String& operator = (const String &s);
    friend std::ostream& operator <<(std::ostream& o, const String &s);
};

/*无参构造*/
String::String():str(NULL){}

/*参数字符串构造*/
String::String(const char* s){
    str = new char[strlen(s) + 1];
    strcpy(str,s);
}

/*拷贝构造*/
String::String(String &s){
    str = new char[strlen(s.str) + 1];
    strcpy(str,s.str);
}

/*析构*/
String::~String(){
    if(str) delete str;
}

/*返回对象的数据成员str*/
const char* String::getStr() const{
    return str;
}

/*重载 = 对象已经存在*/
String& String::operator =(const char*s){
    if(str) delete str;  
        str = new char[strlen(s) + 1];
    strcpy(str,s);
    return *this;
}

/* 重载 =  */
String& String::operator = (const String &s){
    if(this!=&s){
        if(str) delete str;  
        str = new char[strlen(s.str) + 1];
        strcpy(str,s.str);
    }
    return *this;
}

/* 友元函数重载 << */
std::ostream& operator <<(std::ostream& o, const String &s) {    
    o << s.str << std::endl;
    return o;
}

int main() 
{
    
    return 0;
}