C++ Tutorial/string/string

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copy constructor

#include <iostream>
using std::cout;
using std::endl;
#include <string>
using std::string;
int main()
{
   string s1( "AA1234567890asdfasdf" );
   string s2( " AAB" );
   string s3;
   // test copy constructor
   string *s4Ptr = new string( s1 );  
   cout << "\n*s4Ptr = " << *s4Ptr << "\n\n";
   return 0;
}
*s4Ptr = AA1234567890asdfasdf

Create a string from a vector<char>

#include <iostream>
#include <string>
#include <cctype>
#include <algorithm>
#include <vector>
using namespace std;
int main()
{
  string strA("This is a test.");
  // Create a string from a vector<char>.
  vector<char> vec;
  for(int i=0; i < 10; ++i)
    vec.push_back("A"+i);
  string strC(vec.begin(), vec.end());
  cout << "Here is strC, which is constructed from a vector:\n";
  cout << strC << endl;
  return 0;
}

Create a string object using another string object

#include <iostream>
#include <string>
using namespace std;
int main()
{
  string str1("A");
  string str2("B");
  string str3("G");
  string str4;
  cout << "  str1: " << str1 << endl;
  cout << "  str2: " << str2 << endl;
  cout << "  str3: " << str3 << "\n\n";
  // Create a string object using another string object.
  cout << "Initialize str5 with the contents of str1.\n";
  string str5(str1);
  cout << "str5: " << str5 << "\n\n";
  return 0;
}

Define a string variable, assign a value and display it

#include <iostream>
#include <string>
using namespace std ;
using std::cout;       
using std::cin;
int main()
{
  string s = "www.java2s.com \n";
  cout <<s; 
  return 0;
}
www.java2s.com

Input from an istringstream object.

#include <iostream>
#include <string>
#include <sstream>
using namespace std;
main()
{
   string input( "Input test 123 4.7 A" );
   istringstream inputString( input );
   string string1, string2;
   int i;
   double d;
   char c;
   inputString >> string1 >> string2 >> i >> d >> c;
   cout << "The following items were extracted\n"
        << "from the istringstream object:"
        << "\nstring: " << string1 
        << "\nstring: " << string2 
        << "\n   int: " << i 
        << "\ndouble: " << d 
        << "\n  char: " << c;
   // attempt to read from empty stream
   long l;
   if ( inputString >> l )
      cout << "\n\nlong value is: " << l << endl;
   else
      cout << "\n\ninputString is empty" << endl;
   return 0;
}

Loop through the string array

#include <iostream>
#include <list>
#include <algorithm>
#include <string>
using namespace std;
int main( ) {
   string arrStr[5] = {"A", "B", "C", "D", "E"};
   for (string* p = &arrStr[0]; p != &arrStr[5]; ++p) {
      cout << *p << endl;
   }
}
A
B
C
D
E

string basics

#include <iostream>
#include <string>
using namespace std;
int main()
{
  string str1("Alpha");
  string str2("Beta");
  string str3("Omega");
  string str4;
  // assign a string
  str4 = str1; 
  cout << str1 << "\n" << str3 << "\n";
  // concatenate two strings
  str4 = str1 + str2; 
  cout << str4 << "\n";
  // concatenate a string with a C-string
  str4 = str1 + " to " + str3;
  cout << str4 << "\n";
  // compare strings
  if(str3 > str1) cout << "str3 > str1\n";
  if(str3 == str1+str2)
    cout << "str3 == str1+str2\n";
  /* A string object can also be 
     assigned a normal string. */
  str1 = "This is a null-terminated string.\n";
  cout << str1;
  // create a string object using another string object
  string str5(str1);
  cout << str5;
  // input a string
  cout << "Enter a string: ";
  cin >> str5;
  cout << str5;
  return 0;
}
Alpha
Omega
AlphaBeta
Alpha to Omega
str3 > str1
This is a null-terminated string.
This is a null-terminated string.
Enter a string: a string
a

Using a dynamically allocated ostringstream object.

#include <iostream>
#include <string>
#include <sstream>
using namespace std;
main()
{
   ostringstream outputString;
   string s1( "Output of several data types " ),
          s2( "to an ostringstream object:" ),
          s3( "\n        double: " ),
          s4( "\n           int: " ),
          s5( "\naddress of int: " );
   double d = 123.4567;
   int i = 22;
   outputString << s1 << s2 << s3 << d << s4 << i << s5 << &i;
   cout << "outputString contains:\n" << outputString.str();
   outputString << "\nmore characters added";
   cout << "\n\nafter additional stream insertions,\n"
        << "outputString contains:\n" << outputString.str() 
        << endl;
   return 0;
}
Источник — «http://cppe.ru/index.php?title=C%2B%2B_Tutorial/string/string&oldid=2771»