String类的实现

#include<iostream>
using namespace std;

class String
{
public:
String(const char *str = NULL);
String(const String &other);
~String(void);
String & operator=(const String &other);
bool operator==(const String &str);
friend ostream & operator<<(ostream& o,const String &str);
private:
char *m_data;
};

/*
构造、析构、拷贝构造、赋值运、流输出运算
*/

String::String(const char *str)
{
if (str == NULL){
m_data = new char[1];
*m_data='\0';
}else{
int len=strlen(str);
m_data = new char[len+1];
strcpy(m_data,str);
}
}
String::~String(void)
{
delete [] m_data;
}

String::String(const String &other)
{
int len = strlen(other.m_data);
m_data = new char[len+1];
strcpy(m_data,other.m_data);
}

String & String::operator=(const String &other)
{
if (this == &other)
return *this;

delete []m_data;

int len = strlen(other.m_data);
m_data = new char[len+1];
strcpy(m_data,other.m_data);

return *this;
}

bool String::operator==(const String &str)
{
return strcmp(m_data,str.m_data) == 0;
}

ostream & operator<<(ostream &o,const String &str)
{
o<<str.m_data;
return o;

int main()
{
String s = "hello";
String s2 = s;
String ss = "hello";
cout<<"s = "<<s<<endl;
cout<<"s2 = "<<s2<<endl;
cout<<boolalpha<<(ss == s)<<endl;
}