Java Interview Question 2

Package com. softeem. demo;

Import java. io. FileInputStream;
Import java. io. FileNotFoundException;
Import java. io. IOException;
Import java. io. InputStream;
Import java. util. Properties;

/**
* @ Authorleno
* The configuration attribute file is loaded only once during the entire application.
*/
Publicclass Singleton {

Privatestatic Singleton instance;
Privatestaticfinal String CONFIG_FILE_PATH = "E: \ config. properties ";
Private Properties config;
Private Singleton ()
    {
Config = new Properties ();
InputStream is;
Try {
Is = new FileInputStream (CONFIG_FILE_PATH );
Config. load (is );
Is. close ();
} Catch (FileNotFoundException e ){
// TODO Auto-generated catch block
E. printStackTrace ();
} Catch (IOException e ){
// TODO Auto-generated catch block
E. printStackTrace ();
      }
    }
Publicstatic Singleton getInstance ()
    {
If (instance = null)
      {
Instance = new Singleton ();
      }
Returninstance;
    }
Public Properties getConfig (){
Returnconfig;
    }
Publicvoid setConfig (Properties config ){
This. config = config;
    }
   
   

}
L J2SE
19. Copy a directory (file) to the specified path
/**
* Copy a directory or file to a specified path
* @ Paramsource
* @ Paramtarget
*/
Publicvoid copy (File source, File target)
    {
File tarpath = new File (target, source. getName ());
If (source. isDirectory ())
      {
Tarpath. mkdir ();
File [] dir = source. listFiles ();
For (int I = 0; I <dir. length; I ++ ){
Copy (dir [I], tarpath );
          }
} Else
      {
Try {
InputStream is = new FileInputStream (source );
OutputStream OS = new FileOutputStream (tarpath );
Byte [] buf = newbyte [1, 1024];
Int len = 0;
While (len = is. read (buf ))! =-1)
              {
OS. write (buf, 0, len );
              }
Is. close ();
OS. close ();
} Catch (FileNotFoundException e ){
// TODO Auto-generated catch block
E. printStackTrace ();
} Catch (IOException e ){
// TODO Auto-generated catch block
E. printStackTrace ();
          }
      }
    }
20. Example of bank withdrawal using multithreading in JAVA
Packagecom. softeem. demo;

/**
* @ Authorleno
* Account type
* The account has a balance by default and can be withdrawn.
*/
Class Account {
Privatefloatbalance = 1000;

Publicfloat getBalance (){
Returnbalance;
    }

Publicvoid setBalance (float balance ){
This. balance = balance;
    }
   
/**
* The withdrawal method must be synchronized.
* @ Parammoney
*/
Publicsynchronizedvoid withdrawals (float money)
    {
If (balance> = money)
      {
System. out. println ("removed" + money + "RMB! ");
Try {
Thread. sleep (1000 );
} Catch (InterruptedException e ){
// TODO Auto-generated catch block
E. printStackTrace ();
          }
Balance-= money;
      }
Else
      {
System. out. println ("Sorry, the balance is insufficient! ");
      }
    }
   
}

/**
* @ Authorleno
* Bank card
*/
Class TestAccount1 extends Thread {

Private Account account;
   
   
Public TestAccount1 (Account account Account ){
This. account = account;
    }


@ Override
Publicvoid run (){
Account. withdrawals (800 );
System. out. println ("balance:" + account. getBalance () + "RMB! ");
    } 
}
/**
* @ Authorleno
* Passbook
*/
Class TestAccount2 extends Thread {

Private Account account;
Public TestAccount2 (Account account Account ){
This. account = account;
      }
@ Override
Publicvoid run (){
Account. withdrawals (700 );
System. out. println ("balance:" + account. getBalance () + "RMB! ");
    } 
}

Publicclass Test
{
Publicstaticvoid main (String [] args ){
Account account = new Account ();
TestAccount1 testAccount1 = new TestAccount1 (account );
TestAccount1.start ();
TestAccount2 testAccount2 = new TestAccount2 (account );
TestAccount2.start ();
    }
}
21. Example of train station ticket sales using multithreading in JAVA
Package com. softeem. demo;

/**
* @ Authorleno
* Ticket sales
*/
Class SaleTicket implements Runnable {
Inttickets = 100;

Publicvoid run (){
While (tickets> 0 ){
Sale ();
// Or the following implementation
// Synchronized (this ){
// If (tickets> 0 ){
// System. out. println (Thread. currentThread (). getName () + "seller"
// + (100-tickets + 1) + "tickets ");
// Tickets --;
//}
//}
      }
    }

Publicsynchronizedvoid sale (){
If (tickets> 0 ){
System. out. println (Thread. currentThread (). getName () + "seller"
+ (100-tickets + 1) + "tickets ");
Tickets --;
      }
    }

}

Publicclass TestSaleTicket {

Publicstaticvoid main (String [] args ){
SaleTicket st = new SaleTicket ();
New Thread (st, "Window 1"). start ();
New Thread (st, "Window 2"). start ();
New Thread (st, "Window 3"). start ();
New Thread (st, "Window No. 4"). start ();

    }
}

22. Sample producer and consumer issues using multithreading in JAVA
Package com. softeem. demo;

Class Producer implements Runnable
{
Private SyncStack stack;

Public Producer (SyncStack stack ){
This. stack = stack;
}

Publicvoid run (){
For (int I = 0; I <stack. getProducts (). length; I ++ ){
String product = "product" + I;
Stack. push (product );
System. out. println ("produced:" + product );
Try
          {
Thread. sleep (200 );
          }
Catch (InterruptedException e)
          {
E. printStackTrace ();
          }


      }
    }
   
}

Class Consumer implements Runnable
{
Private SyncStack stack;

Public Consumer (SyncStack stack ){
This. stack = stack;
}
Publicvoid run (){
For (int I = 0; I <stack. getProducts (). length; I ++)
          {
String product = stack. pop ();
System. out. println ("consumed:" + product );
Try
          {
Thread. sleep (1000 );
          }
Catch (InterruptedException e)
          {
E. printStackTrace ();
          }

          }

     
    }
}

Class SyncStack
{
Private String [] products = new String [10];
Privateintindex;
Publicsynchronizedvoid push (String product)
    {
If (index = product. length ())
      {
Try {
Wait ();
} Catch (InterruptedException e ){
// TODO Auto-generated catch block
E. printStackTrace ();
          }
      }
Notify ();
Products [index] = product;
Index ++;
    }
   
Publicsynchronized String pop ()
    {
If (index = 0)
      {
Try {
Wait ();
} Catch (InterruptedException e ){
// TODO Auto-generated catch block
E. printStackTrace ();
          }
      }
Notify ();
Index --;
String product = products [index];
Return product;
    }

Public String [] getProducts (){
Returnproducts;
    }
   
   
}
Publicclass TestProducerConsumer {
   
Publicstaticvoid main (String [] args ){
SyncStack stack = new SyncStack ();
Producer p = new Producer (stack );
Consumer c = new Consumer (stack );

New Thread (p). start ();
New Thread (c). start ();
      }
    }