Refined Readers Writers solution

Here's an improved version of Readers writers where i have used Semaphore class provide in java.util.concurrent package . . . Tell me if any changes required

ReadersWriters.java

import java.util.Scanner;

import java.util.concurrent.Semaphore;

public class ReadersWriters

{

public static void main(String[] args)

{

System.out.println("Enter the number of Readers : ");

Scanner sc = new Scanner(System.in);

int totalReaders = sc.nextInt();

Reader reader[] = new Reader[totalReaders];

System.out.println("Enter the number of Writers : ");

int totalWriters = sc.nextInt();

Writer writer[] = new Writer[totalWriters];

Database db = new Database(0);

Semaphore semDB = new Semaphore(1);

Semaphore semRC = new Semaphore(1);

for(int i=0;i<totalReaders;i++)

{

reader[i] = new Reader(i,db,semRC,semDB);

new Thread(reader[i]).start();

}

for(int i=0;i<totalWriters;i++)

{

writer[i] = new Writer(i,db,semDB);

new Thread(writer[i]).start();

}

}

}

class Reader implements Runnable

{

int rno;

Database db;

Semaphore semDB;

Semaphore semRC;

Reader(int rno, Database db, Semaphore semDB, Semaphore semRC)

{

this.rno = rno;

this.db = db;

this.semDB = semDB;

this.semRC = semRC;

}

public void run()

{

try{

semRC.acquire(); //acquire lock on reader Count

db.rc++; //Increment Reader Count

semRC.release(); // release the lock on reader count

if(db.rc == 1) // Check if only one reader

{

db.rc--;

semDB.acquire(); // Acquire lock on value of database or Enter the Critical section

System.out.println("Value read by the reader "+this.rno+" is :"+db.read());

Thread.sleep(2000);

semDB.release(); // Exit from the critical section

}

}

catch(InterruptedException ie)

{

ie.printStackTrace();

}

}

}

class Writer implements Runnable

{

int wno;

Database db;

Semaphore semDB;

Writer(int wno, Database db,Semaphore semDB)

{

this.wno = wno;

this.db = db;

this.semDB = semDB;

}

public void run()

{

try{

semDB.acquire(); // Entering the Critical Section

System.out.println("Writer "+this.wno+" is writing value "+(this.wno+10)+" to the Database...");

db.write(this.wno+10); // Writing the value to the Database

Thread.sleep(2000);

semDB.release(); // leaving the Critical Section

}

catch(InterruptedException ie)

{

ie.printStackTrace();

}

}

}

class Database

{

int value;

int rc;

Database(int value)

{

this.value = value;

this.rc = 0;

}

int read()

{

return this.value;

}

void write(int value)

{

this.value = value;

}

}