C++之string

/*
 * 版权所有  公众号  VxWorks567
 */
#include <string>
#include <iostream>
#include <stdio.h>

using namespace std;

int testStr()
{
    const char *chars1 = "ccc";
    char chars2[] = "ddd";
    string str1;
    string str2;

    // 使用字符常量初始化string
    str1 = chars1;

    // 使用字符数组初始化string
    str2 = chars2;

    string str = "Hello World";
    // cout直接输出string的字符
    cout << "cout: " << str << endl;

    // c_str()将string 转换为 char*
    const char *chars = str.c_str();
    printf("printf: %s\n", chars);
 
    // empty()判断string是否为空
    cout << "empty: " << str.empty() << endl;

    // compare()判断两个string是否相同
    cout << "compare: " << str.compare("Hello Worl") << endl;
    cout << "compare: " << str.compare("Hello World") << endl;
    cout << "compare: " << str.compare("Hello Worldd") << endl;

    // length()/size()计算string的字符数量
    cout << "length: " << str.length() << endl;

    // max_size()返回string的字符容量
    cout << "max_size: " << hex << str.max_size() << endl;

    // resize()调整string的长度, 变长则追加, 变短则截取
    str.resize(str.size()+2, 'x');
    cout << "resize: " << str << endl;

    // push_back()表示追加1个字符
    str.push_back('y');
    cout << "push_back: " << str << endl;

    // append()表示追加string或多个字符
    cout << "append: " << str.append(str1) << endl;
    cout << "append: " << str.append(2, 'a') << endl;

    // replace()表示替换
    cout << "replace: " << str.replace(str.size()-2, 2, "zz") << endl;

    // insert()表示插入
    str.insert(str.size()-2, "ww");
    cout << "insert: " << str << endl;

    // erase()表示删除
    cout << "erase: " << str.erase(str.size()-5, 5) << endl;

    // find()在string中查找子串出现的位置
    cout << "find: " << str.find("llo") << endl;
    // 子串不存在就返回npos, 值为0xffffffff
    cout << "find: " << hex << str.find("lmn") << endl;

    // rfind()在string中由右向左查找子串出现的位置
    cout << "rfind: " << dec << str.rfind("l") << endl;

    // find_first_of()在string中查找子串中的任意字符第一次出现的位置
    cout << "find_first_of: " << str.find_first_of("lmn") << endl;

    // find_last_of()在string中查找子串中的任意字符最后一次出现的位置
    cout << "find_last_of: " << str.find_last_of("lmn") << endl;

    // find_first_not_of()在string中查找第一个不同于子串任意字符的字符位置
    cout << "find_first_not_of: " << str.find_first_not_of("lmn") << endl;

    // find_last_not_of()在string中查找最后一个不同于子串任意字符的字符位置
    cout << "find_last_not_of: " << str.find_last_not_of("lmn") << endl;

    // substr()返回string的子串
    cout << "substr: " << str.substr(1, 4) << endl;

    // swap()交换string
    cout << "before swap: " << str << " " << str1 << endl;
    str.swap(str1);
    cout << "after swap: " << str << " " << str1 << endl;

    // assign()表示赋值
    cout << "assign: " << str.assign(str2) << endl;

    // +表示连接
    cout << "+: " << str+str1 << endl;

    // []表示取成员
    cout << "[]: " << str[1] << endl;

    // clear()表示清空
    str.clear();
    cout << "clear: " << str << endl;

    return 0;
    }