STL string output and modification

1、string Output

#include <iostream>
using namespace std;

void StrCout()
{
    string str2("ojkojkojk");
    cout << str2 << endl;
    cout << str2.c_str() << endl;
    cout << str2[0] << endl;
    cout << str2.at(3)<< endl;//at() Function returns a reference , Point at index The character of position ( Subscript ), If index Not within the string range ,at（） Will report “out f range” error
    // Cross the border
    try
    {
        str2.at(19);
    }
    /*catch (...)
    {
        cout << " Across the border \n";
    }*/
    catch (out_of_range& a)
    {
        cout << " Across the border \n";
    }
}
int main()
{
    StrCout();
    system("pause");
    return 0;
}

2、

#include <iostream>
using namespace std;

void StrCout()
{
    string str2("ojkojkojk");
    cout << str2 << endl;
    cout << str2.c_str() << endl;
    cout << str2[0] << endl;
    cout << str2.at(3) << endl;//at() Function returns a reference , Point at index The character of position ( Subscript ), If index Not within the string range ,at（） Will report “out f range” error
    // Cross the border
    try
    {
        str2.at(19);
    }
    /*catch (...)
      {
    cout << " Across the border \n";
      }*/
    catch (out_of_range& a)
    {
        cout << " Across the border \n";
    }
}
void StrChange()
{
    string str2("ojkojkojk");// Change
    /*str2[2] = 's';
    str2.at(3) = 'q';// Replace */

    //string str3(5, 'q');// increase
    string str3("abcdefg");//insert function . Insert
    //str2.insert(2, str3);// take str3 Insert the subscript as 2 The location of .
    //str2.insert(2, "akfdsks");// Insert the string with the subscript 2 The location of .
    //str2.insert(3, str3,0,2);// take str3 Subscript is [0,2) Insert str2 The subscript in is 3 The location of .
    //str2.insert(3,"sjhdfja", 2);// Subscript the string as [0,2) Insert str2 The subscript in is 3 The location of .
    //str2.insert(3, 2, 'b');// stay str2 The subscript of is 3 Insert at 2 individual b.
    
    //str2 += str3;// Add... At the end .// increase
    //str2 += "sjhasd";// Add... At the end .

    //append function // Add... At the end , And insert The approximate , What is inserted is the end .// increase
    //str2.append(str3);
    //str2.append("sdhasjj",3);// The first three are added to str2 after
    //str2.append(3,'w');// Will three w Add to str2 after

    // Reassign // Change
    //str2 = "qwer";
    //str2 = str3;
    //cin>>str2;
    //str2.assign("ashjd", 2);// And insert and append The usage is the same .

    // Delete
    //str2.erase(2,3);// stay str2 From the subscript is 2 To delete 3 Characters .
    str2.erase(0,str2.length());// Delete all characters .
    cout << str2 << endl;

}

int main()
{
    //StrCout();
    StrChange();
    system("pause");
    return 0;
}