自定义实现String类

来源：互联网发布：php数据库输出乱码编辑：程序博客网时间：2024/04/27 09:15
自定义实现String类的内容
直接在代码中阐述：附有测试样例
代码：
#include <iostream>//#include <cstring>using namespace std;class String{    public:        //ctor        String();        String(const char* s);        String(const char* s, size_t len);        String(const String& rhs);        String(size_t Len);        String& operator=(const String& rhs);        //dtor        ~String();        //get        size_t size() const;        const char* data() const;        const char* c_str() const;        // set & get        char & operator[](size_t index);        char operator[] (size_t index) const;        //imp        String operator +(const String& rhs);        void operator +=(const String& rhs);        //输出        friend ostream& operator <<(ostream& out,const String& rhs);    private:        char*  data_;        size_t len_;};    String::String()        : data_(NULL), len_(0)    {        data_ = new char[1];        data_[0] = '\0';    }    String::String(size_t Len)    {        data_ = new char[Len+1];        for(size_t i=0;i<=Len;i++)        {            data_[i] = '\0';        }    }    String::String( const char* s )    {        size_t i = 0;        size_t len = 0;        while(s[i] != '\0')        {            i++;            len++;        }        data_ = new char[len+1];        for(size_t j = 0;j < len;j++)        {            data_[j] = s[j];        }        data_[len] = '\0';        len_ = len;    }    String::String( const char* s, size_t len )    {        data_ = new char[len+1];        for(size_t k=0;k<len;k++)        {            data_[k] = s[k];        }        data_[len] = '\0';        len_ = len;    }    String::String( const String& rhs )    {        size_t len = rhs.size();        data_ = new char[len+1];        for(size_t i=0;i<len;i++)        {            data_[i] = rhs.data_[i];        }        data_[len] = '\0';        len_ = len;    }    String String::operator +(const String& rhs)    {        size_t totalLen = len_ + rhs.len_;        String tmp(totalLen);        size_t i,j;        for(i=0;i<len_;i++)        {            tmp[i] = data_[i];        }        for(j=0;j<rhs.len_;j++,i++)        {            tmp[i] = rhs.data_[j];        }        return tmp;    }    void String::operator +=(const String& rhs)    {        size_t totalLen = len_ + rhs.len_;        String tmp(totalLen);        size_t i,j;        for(i=0;i<len_;i++)        {            tmp[i] = data_[i];        }        for(j=0;j<rhs.len_;j++,i++)        {            tmp[i] = rhs.data_[j];        }        *this = tmp;    }    String& String::operator=( const String& rhs )    {        //比较对象的地址        if(this == &rhs)        {            return *this;        }        delete[] data_;        size_t len = rhs.size();        data_ = new char[len+1];        for(size_t i = 0;i < len; i++)        {            data_[i] = rhs.data_[i];        }        data_[len] = '\0';        return *this;    }    String::~String()    {        if(data_)        {            delete[] data_;            data_ = NULL;        }        len_ = 0;    }    size_t String::size() const    {        int i = 0;        int len_ = 0;        while(data_[i] != '\0')        {            i++;            len_++;        }        return len_;    }    const char* String::data() const    {        return data_;    }    const char* String::c_str() const    {        return data_;    }    char & String::operator[](size_t index )    {        if(index > len_)        {            return data_[len_-1];        }        else        {            return data_[index];        }    }    char String::operator[] (size_t index) const    {        if(index > len_)        {            return data_[len_-1];        }        else        {            return data_[index];        }    }    //注意 友员不是成员函数 不用加上String::    ostream& operator <<(ostream& out,const String& rhs)    {        out<< rhs.data_ << endl;        return out;    }int main(){    String a("hello",3);    cout << a ;    String b("world");    String c(b);    cout << c ;    cout << c[2] <<endl;    cout << a+b;    //cout << a << endl;    //cout << a+b << endl;    /*    String a("hello");    cout << a << endl; //这个是 重载的 <<    char x[20];    String c = "wolrd";    strcpy(x,c.c_str());    cout << x << endl;    cout << "Hello world!" << endl;    return 0;    */}
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