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  1. import java.util.Scanner;
  2. import java.util.StringTokenizer;
  3. import java.util.Vector;
  4. import java.util.TreeMap;
  5. import java.lang.NumberFormatException;
  6.  
  7. public class Main
  8. {
  9.    //структура, описывающая атрибуты учетной записи
  10.    public class AccountInfo
  11.    {
  12.       public String password;
  13.       public boolean loggedIn;
  14.  
  15.       public AccountInfo(String argPassword, boolean argLoggedIn)
  16.       {
  17.          password = argPassword;
  18.          loggedIn = argLoggedIn;
  19.       }
  20.    }
  21.  
  22.  
  23.    //база данных учетной записи
  24.    public class AccountDatabase
  25.    {
  26.       public static final int OK = 0;
  27.       public static final int NOT_REGISTERED = 1;
  28.       public static final int WRONG_PASSWORD = 2;
  29.       public static final int ALREADY_LOGGED_IN = 3;
  30.       public static final int ALREADY_LOGGED_OUT = 4;
  31.  
  32.       private TreeMap<String, AccountInfo> map;
  33.  
  34.       //конструктор
  35.       public AccountDatabase()
  36.       {
  37.          map = new TreeMap<String, AccountInfo>();
  38.       }
  39.  
  40.       //регистрация новой учетной записи
  41.       public boolean register(String name, String password)
  42.       {
  43.          AccountInfo info = map.get(name);
  44.  
  45.          if (info != null)
  46.          {
  47.             return false;
  48.          }
  49.  
  50.          map.put(name, new AccountInfo(password, false));
  51.  
  52.          return true;
  53.       }
  54.  
  55.       //вход в систему
  56.       public int login(String name, String password)
  57.       {
  58.          int result = NOT_REGISTERED;
  59.  
  60.          AccountInfo info = map.get(name);
  61.  
  62.          if (info != null)
  63.          {
  64.             if (!info.password.equals(password))
  65.             {
  66.                result = WRONG_PASSWORD;
  67.             }
  68.             else if (info.loggedIn)
  69.             {
  70.                result = ALREADY_LOGGED_IN;
  71.             }
  72.             else
  73.             {
  74.                map.put(name, new AccountInfo(info.password, true));
  75.                result = OK;
  76.             }
  77.          }
  78.  
  79.          return result;
  80.       }
  81.  
  82.       //выход из системы
  83.       public int logout(String name)
  84.       {
  85.          int result = NOT_REGISTERED;
  86.  
  87.          AccountInfo info = map.get(name);
  88.  
  89.          if ( info != null )
  90.          {
  91.             if ( info.loggedIn )
  92.             {
  93.                map.put(name, new AccountInfo(info.password, false));
  94.                result = OK;
  95.             }
  96.             else
  97.             {
  98.                result = ALREADY_LOGGED_OUT;
  99.             }
  100.          }
  101.  
  102.          return result;
  103.       }
  104.  
  105.    }
  106.  
  107.    public static void main(String[] args)
  108.    {
  109.       int loginCount = 0;
  110.       String line = null;
  111.  
  112.       Scanner in = new Scanner(System.in);
  113.       //System.out.println("please enter number of logins: ");
  114.       line = ( in.hasNextLine( ) ) ? in.nextLine() : null;
  115.       try
  116.       {
  117.          loginCount = Integer.parseInt(line.trim());
  118.       }
  119.       catch( NumberFormatException e )
  120.       {
  121.       }
  122.  
  123.       if ( loginCount < 1 || loginCount > 100 )
  124.       {
  125.          System.out.println("**** ERROR: wrong number of logins ****");
  126.          in.close();
  127.          return;
  128.       }
  129.  
  130.       Main mainObj = new Main();
  131.       AccountDatabase accounts = mainObj.new AccountDatabase();
  132.  
  133.       for( int i = 0; i < loginCount; i++ )
  134.       {
  135.          //System.out.println("please enter command:");
  136.  
  137.          line = ( in.hasNextLine( ) ) ? in.nextLine() : null;
  138.          if ( line == null || line.isEmpty() )
  139.          {
  140.             System.out.println("**** ERROR: empty input, abort processing ****");
  141.             break;
  142.          }
  143.  
  144.          //превращение введенной строки текста в вектор лексем
  145.          StringTokenizer st = new StringTokenizer(line, " ");
  146.          Vector<String> tokens = new Vector<String>();
  147.          while (st.hasMoreTokens())
  148.          {
  149.             tokens.add( st.nextToken() );
  150.          }
  151.  
  152.          //превращение вектора лексем в команду с аргументами
  153.          String command   = ( tokens.size() > 0 ) ? tokens.get(0) : null;
  154.          String name      = ( tokens.size() > 1 ) ? tokens.get(1) : null;
  155.          String password  = ( tokens.size() > 2 ) ? tokens.get(2) : null;
  156.          String message = null;
  157.  
  158.         //выполнение команд
  159.          if ( command.equals("register"))
  160.          {
  161.             if ( name != null || password != null )
  162.             {
  163.                if ( accounts.register(name, password) )
  164.                {
  165.                   message = "success: new user added";
  166.                }
  167.                else
  168.                {
  169.                   message = "fail: user already exists";
  170.                }
  171.             }
  172.             else
  173.             {
  174.                message = "fail: missing user name or password";
  175.             }
  176.          }
  177.          else if ( command.equals("login"))
  178.          {
  179.             if ( name != null || password != null )
  180.             {
  181.                switch( accounts.login(name, password) )
  182.                {
  183.                   case AccountDatabase.NOT_REGISTERED:
  184.                      message = "fail: no such user";
  185.                   break;
  186.                   case AccountDatabase.WRONG_PASSWORD:
  187.                      message = "fail: incorrect password";
  188.                   break;
  189.                   case AccountDatabase.ALREADY_LOGGED_IN:
  190.                      message = "fail: already logged in";
  191.                   break;
  192.                   default:
  193.                      message = "success: user logged in";
  194.                   break;
  195.               }
  196.            }
  197.            else
  198.            {
  199.               message = "fail: missing user name or password";
  200.            }
  201.          }
  202.          else if ( command.equals("logout"))
  203.          {
  204.             if ( name != null )
  205.             {
  206.                switch( accounts.logout(name) )
  207.                {
  208.                   case AccountDatabase.ALREADY_LOGGED_OUT:
  209.                      message = "fail: already logged out";
  210.                   break;
  211.                   case AccountDatabase.NOT_REGISTERED:
  212.                      message = "fail: no such user";
  213.                   break;
  214.                   default:
  215.                      message = "success: user logged out";
  216.                   break;
  217.                }
  218.             }
  219.             else
  220.             {
  221.                message = "fail: missing user name";
  222.             }
  223.          }
  224.  
  225.          if ( message != null )
  226.          {
  227.             System.out.println(message);
  228.          }
  229.       }
  230.       in.close();
  231.    } 
  232. }
  233.  
Runtime error #stdin #stdout #stderr 0.14s 321280KB
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Standard input is empty
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Standard output is empty
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Exception in thread "main" java.lang.NullPointerException
	at Main.main(Main.java:117)
https://ideone.com/3Y2W4z
language:
Java (12.0.1)
created:
8 years ago
visibility:
secret

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