一个string类的简单实现

string类中使用到了赋值构造函数、复制构造函数、构造函数、默认构造函数、析构函数、重载操作符等一些类操作

class String
{
	public:
		String()
		{
			data = new char;
			data[0]='\0';
			length = 0;
		}
		String(const char* str)
		{
			length = strlen(str);
			data = new char[length+1];
			strcpy(data,str);
			data[length]='\0';
		}
		String(const char* str,int n)
		{
			length = n;
			data = new char[n+1];
			strncpy(data,str,n);
			data[length] ='\0';
		}
		String(const String& src)
		{
			length = src.length;
			data = new char[length+1];
			strcpy(data,src.data);
		}
		String& operator=(const String& src)
		{
			if(this == &src)
				return *this;
			delete [] data;
			data = new char[src.length+1];
			strcpy(data,src.data);
			return *this;
		}
		String& operator=(const char* src)
		{
			delete [] data;
			length = strlen(src);
			data = new char[length+1];
			strcpy(data,src);
			return *this;
		}
		char& operator[](int n)
		{
			return data[n];
		}
		const char& operator[](int n) const
		{
			return str[n];
		}
		ostream& operator<<(ostream& os,const string& st)
		{
			os<<st.data<<endl;
			return os;
		}
		~String()
		{
			delete [] data;
		}
	private:
		char* data;
		int length;
};