c++实现String类（构造函数，析构函数，复制构造函数，各类运算符重载函数的编写）

编写类 String 的构造函数，析构函数，复制构造函数 

需要重载下面的运算符：

1、<、>、==和！=比较运算符

2、+=连接运算符和赋值运算符

3、<<输出运算符和>>输入运算符

String.h

#ifndef _STRING_H_  #define _STRING_H_  #include <iostream>  using namespace std;class String{public:String();//默认构造函数String(int n,char c);//普通构造函数String(const char* source);//普通构造函数String(const String& s);//复制构造函数    ~String();//析构函数    String& operator=(char* s);//重载=，实现字符串赋值String& operator=(const String& s);//重载=，实现对象赋值char& operator[](int i);//重载[]，实现数组运算const char& operator[](int i)const;//重载[]，实现数组运算（对象为常量）String& operator += (const String& s);//重载+=，实现与对象相加String& operator += (const char* s);//重载+=，实现与字符串相加friend ostream& operator << (ostream &out, String& s);//重载<<，实现输出流friend istream& operator >> (istream &in, String& s);//重载>>，实现输入流friend bool operator < (const String& left, const String& right);//重载<friend bool operator > (const String& left, const String& right);//重载>friend bool operator == (const String& left, const String& right);//重载==friend bool operator != (const String& left, const String& right);//重载！=//char* getData();//获取data指针int length();                   //获取字符串长度private:int size;       //data表示的字符长度char* data;     //指向字符串数据};#endif 

String.cpp

#include <iostream>  #include <string.h>  #include "String.h"  using namespace std;String::String(){             //默认构造函数,构造空字符串data = new char[1];       //空字符串只有'\0'一个元素*data = '\0';size = 0;}String::String(int n, char c){  //普通构造函数data = new char[n+1];       //含有N个相同字符的字符串size = n;char* temp = data;          //保存datawhile (n--)                 //做n次赋值 {*temp++ = c;}*temp = '\0';}String::String(const char* source){//普通构造函数if (source ==NULL)          //字符串内容与source相同{data = new char[1];       //将data赋为空字符串*data = '\0';size = 0;}else{size = strlen(source);  //复制source字符串data = new char[size + 1];strcpy(data, source);}}String::String(const String& s){    //复制构造函数data = new char[s.size + 1];     //字符串内容与对象s的相同strcpy(data, s.data);size = s.size;}String::~String(){//析构函数if (data != NULL)          //字符串内容与source相同{delete []data;       //data不为空，释放堆内存data = NULL;size = 0;}}String& String::operator=(char* s){//重载=，实现字符串赋值if (data != NULL)          {delete[]data;       }size = strlen(s);data = new char[size + 1];strcpy(data, s);   //复制目标字符串return *this;}String& String::operator=(const String& s){//重载=，实现String对象赋值if (this == &s)          //如果对象S就是自己，直接返回*this{return *this;}if (data != NULL)     //释放data堆内存{delete[]data;}size = strlen(s.data);data = new char[size + 1];  //分配堆内存strcpy(data, s.data);   //复制对象s的字符串成员return *this;}char& String::operator[](int i){//重载[]，实现数组运算return data[i];             //取数组下标为i的字符元素}const char& String::operator[](int i)const{//重载[]，实现数组运算（对象为常量）return data[i];}String& String::operator += (const String& s){//重载+=，实现与对象相加int len = size + s.size + 1;             //连接对象s的字符串成员char *temp = data;data = new char[len];                     //申请足够的堆内存来存放连接后的字符串size = len - 1;strcpy(data, temp);                       //复制原来的字符串strcat(data, s.data);                     //连接目标对象内的字符串成员delete[] temp;return *this;}String& String::operator += (const char* s){//重载+=，实现与字符串相加if (s == NULL)                             //连接s字符串{return *this;}int len = size + strlen(s) + 1;              char *temp = data;data = new char[len];                       //申请足够的堆内存来存放连接后的字符串size = len - 1;strcpy(data, temp);                         //复制原来的字符串strcat(data, s);                            //连接目标对象内的字符串成员delete[] temp;return *this;}int String::length(){                    //获取字符串长度return size;}ostream& operator << (ostream &out, String& s){//重载<<，实现输出流for (int i = 0; i < s.length();i++)    //打印对象s内字符串成员的所有字符元素 { out << s[i]<<" "; //输出字符串中每一个字符元素 }           return out;}istream& operator >> (istream &in, String& s){//重载>>，实现输入流char p[50];             in.getline(p, 50); //从输入流接收最多50个字符s = p;             //调用赋值函数return in;}bool operator < (const String& left, const String& right){//重载<int i = 0;while (left[i] == right[i] && left[i] !=0&& right[i]!=0){i++;}return left[i] - right[i]<0 ? true : false;}bool operator > (const String& left, const String& right){//重载>int i = 0;while (left[i] == right[i] && left[i] != 0 && right[i] != 0){i++;}return left[i] - right[i] > 0 ? true : false;}bool operator == (const String& left, const String& right){//重载==int i = 0;while (left[i] == right[i] && left[i] != 0 && right[i] != 0){i++;}return left[i] - right[i] == 0 ? true : false;}bool operator != (const String& left, const String& right){//重载！=int i = 0;while (left[i] == right[i] && left[i] != 0 && right[i] != 0){i++;}return left[i] - right[i] != 0 ? true : false;}

Main.cpp

#include <iostream>  #include "String.h"  using namespace std; int  main(void){String str(3,'a'); //普通构造函数测试  String str1(str); //复制构造函数测试String str2("asdf"); //普通构造函数  String str3; //默认构造函数测试 cout << "str:" << str<< endl;cout << "str1:" << str1 << endl;cout << "str2:" << str2 << endl;cout << "str3:" << str3 << endl;str3 = str2;  //赋值函数测试cout << "str3:" << str3 << endl;str3 = "12ab";  //赋值函数测试cout << "str3:" << str3 << endl;cout << "str3[2]:" << str3[2] << endl;// []重载函数测试str3 += "111";  // +=重载函数测试cout << "str3:" << str3 << endl;str3 += str1;   // +=重载函数测试cout << "str3:" << str3 << endl;cin >> str1; // >>重载函数测试cout << "str1:" << str1 << endl;String t1="1234";String t2 = "1234";String t3 = "12345";String t4 = "12335"; cout << "t1 == t2?" << (t1 == t2) << endl;// ==重载函数测试cout << "t1 < t3?" << (t1 < t3) << endl;// <重载函数测试cout << "t1 > t4?" << (t1> t4) << endl;// >重载函数测试cout << "t1 != t4?" << (t1 != t4) << endl;// !=重载函数测试system("pause");return 0;}

结果：