简写string类

#include <iostream>
using namespace std;
class String
{
public:
 String();
 ~String();
 String(const String&rs);
 String(const char*const ch);
 char&operator[](unsigned short int length);
 char operator[](unsigned short int length)const;
 String&operator=(const String&s);
 String operator+(const String &);
 void operator+=(const String&rs);
 //↓重载左移运算符实现字符串输出
 friend ostream &operator<<(ostream & o,const String &str)
 {
  o<<str.str;
  return o;
 }
 //↓重载右移运算符实现字符串输入
 friend istream &operator>>(istream & i,const String &str)
 {
  i>>str.str;
  return i;
 }
 friend bool operator<(const String&str1,const String &str2)
 {
  if(strcmp(str1.str,str2.str)<0)
   return 1;
  else
   return 0;
 }
 friend bool operator>(const String&str1,const String &str2)
 {
  if(strcmp(str1.str,str2.str)>0)
   return 1;
  else
   return 0;
 }
 friend bool operator==(const String&str1,const String &str2)
 {
  if(strcmp(str1.str,str2.str)==0)
   return 1;
  else
   return 0;
 }
 unsigned short int getlen()const{return len;}//获取字符串长度
 const char*getstr()const{return str;}        //获取字符串内容
private:
 String(unsigned short int length);
 unsigned short int len;              //用作计算字符长度
 char*str;                            //  用于保存字符串
};
String::String(unsigned short int length)        //设置字符串长度
{
 str=new char[length+1];                     //给字符串开辟相应的空间+1是用来保存结束符
 int i;
 for(i=0;i<=length;i++)
  str[i]='\0';                         //最好一个元素保存结束符
 len=length;                              //返回字符串长度
}
String::String()             //空的字符串
{
 len=0;                   //空的字符串长度应为0
 str=new char[1];
 str[0]='0';
}
String::~String()            //删除字符串
{
 len=0;
 str=new char[1];
 str[0]='0';
}
String::String(const String&rs)         //复制字符串对象
{
 len=rs.getlen();
 str=new char[len+1];
 for(int i=0;i<len;i++)
  str[i]=rs[i];
 str[len]='\0';
}
String::String(const char*const ch)     //复制字符串
{
 len=strlen(ch);
 str=new char[len+1];
 for(int i=0;i<len;i++)
  str[i]=ch[i];
 str[len]='\0';
}
char&String::operator [](unsigned short int length)        //限制数组
{
 if(length>len)
  return str[len-1];
 else
  return str[length];
}
char String::operator [](unsigned short int length)const      //假如参数是一个常量
{
 if(length>len)
  return str[len-1];
 else
  return str[length];
}
String&String::operator =(const String&s)         
{
 if (this==&s)
  return *this;
 delete[]str;
 len=s.getlen();
 str=new char[len+1];
 for(int i=0;i<len;i++)
 {
  str[i]=s[i];
 }
 str[len]='\0';
 return *this;
}
String String::operator +(const String&rs)
{
 int total=len+rs.getlen();
 String temp(total);
 int i,j;
 for (i=0;i<len;i++)
  temp[i]=str[i];
 for (j=0;j<rs.getlen();j++,i++)
  temp[i]=rs[j];
 temp[total]='\0';
 return temp;
}
void String::operator +=(const String&rs)
{
 int total=len+rs.getlen();
 String temp(total);
 int i,j;
 for (i=0;i<len;i++)
  temp[i]=str[i];
 for (j=0;j<rs.getlen();j++,i++)
 {
  temp[i]=rs[j];
  temp[total]='\0';
  *this=temp;
 }
}
int main()
{
 return 0;
}