Java

a java project on us reservation sytem

public class ReaderWriter{

   public static void main(String args[]){
	   
	   ReadWriteLock RW = new ReadWriteLock();
	   ExecutorService executorService = Executors.newCachedThreadPool();
  
	   executorService.execute(new Writer(RW));
		executorService.execute(new Writer(RW));
		executorService.execute(new Writer(RW));
		executorService.execute(new Writer(RW));
		
		executorService.execute(new Reader(RW));
		executorService.execute(new Reader(RW));
		executorService.execute(new Reader(RW));
		executorService.execute(new Reader(RW));

  }
}
//Writer class
class Writer implements Runnable
{
   private ReadWriteLock rwlock;
   private int writerNum;

    public Writer(int w, ReadWriteLock rw) {
      writerNum = w;
      rwlock = rw;
   }

    public void run() {
      while (true){
         SleepUtilities.nap();
      
         System.out.println("writer " + writerNum + " wants to write.");
         rwlock.WriteLock(writerNum);

         SleepUtilities.nap();
      
         rwlock.WriteUnLock(writerNum);
      }
   }
}

//Reader class
class Reader implements Runnable
{

   private ReadWriteLock rwlock;
   private int readerNum;

    public Reader(int readerNum, ReadWriteLock database) {
      this.readerNum = readerNum;
      this.rwlock = database;
   }

    public void run() {
      while (true) {
         SleepUtilities.nap();
         System.out.println("reader " + readerNum + " wants to read.");
         rwlock.ReadLock(readerNum);
      
      // you have access to read from the database
      // let's read for awhile .....
         SleepUtilities.nap();
      
         rwlock.ReadUnLock(readerNum);
      }
   };
}

//Lock class
class ReadWriteLock {
    private int readerCount;
    private Semaphore mutex; 
    private Semaphore rwlock;     
 
     public ReadWriteLock() {
       readerCount = 0;
       mutex = new Semaphore(1);
       rwlock = new Semaphore(1);
    }
 
     public void ReadLock(int readerNum) {
       try{
          mutex.acquire();
       }
           catch (InterruptedException e) {
        	   
           }
       ++readerCount;
    

       if (readerCount == 1){
          try{
        	  rwlock.acquire();
          }
              catch (InterruptedException e) {
            	  
              }
       }
    
       System.out.println("Reader " + readerNum + " is reading. Reader count = " + readerCount);
       mutex.release();
    }
 
     public void ReadUnLock(int readerNum) {
       try{
          mutex.acquire();
       }
           catch (InterruptedException e) {}
    
       --readerCount;

       if (readerCount == 0){
    	   rwlock.release();
       }
    
       System.out.println("Reader " + readerNum + " is done reading. Reader count = " + readerCount);

       mutex.release();
    }
 
     public void WriteLock(int writerNum) {
       try{
    	   rwlock.acquire();
       }
           catch (InterruptedException e) {}
       System.out.println("Writer " + writerNum + " is writing.");
    }
 
     public void WriteUnLock(int writerNum) {
       System.out.println("Writer " + writerNum + " is done writing.");
       rwlock.release();
    }
 }
class SleepUtilities
{
    public static void nap() {
      nap(NAP_TIME);
   }

    public static void nap(int duration) {
      int sleeptime = (int) (NAP_TIME * Math.random() );
      try { RW.sleep(sleeptime*1000); }
          catch (InterruptedException e) {}
   }

   private static final int NAP_TIME = 5;
}