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

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

String &String::operator=(const String &other)
{
	if(this==&other)
		return *this;
	delete [] m_data;
	int length=strlen(other.m_data);
	m_data=new char[length+1];
	strcpy(m_data,other.m_data);
	return *this;
}