Reader Writer.java

// Code No:-1

import java.util.*;
import java.util.concurrent.Semaphore;
public class Main {
  
static int mutex=1;
static int database=1;
static int Read_Count=0;
static void Reader() throws Exception
{
while(true)
{
mutex=wait(mutex);
Read_Count=Read_Count+1;
if(Read_Count==1){
database=signal(database);
}
mutex=signal(mutex);
System.out.println(Read_Count+ " User Reading the Data.........");
mutex=wait(mutex);
Read_Count=Read_Count-1;
if(Read_Count==0)
{
database=signal(database);
}
mutex=signal(mutex);
System.out.println("Reading Finished!!!!!!");
break;
}
}
static int wait(int mutex)
{
while(mutex<=0)
break ;
mutex=mutex-1;
return mutex;
}
static int signal(int database)
{
database=database+1;
return database;
}
static void Writer() throws Exception
{
while(true)
{
database=wait(database);
System.out.println("Writing on the database......");
database=signal(database);
System.out.println("Writing Finished!!!!!.");
break;
}
}
public static void main(String[] args)throws Exception {
Writer();
Reader();
Reader();
}
}


// Code No:-2

import java.util.concurrent.Semaphore;
import java.util.Scanner;
public class Main {

 static Semaphore mutex = new Semaphore(1);
 static Semaphore wrt = new Semaphore(1);
 static int readCount = 0;
 static String message = "Hello";
 static Scanner SC = new Scanner(System.in);
 static class Reader implements Runnable {
 public void run() {
 try {
 mutex.acquire();
 readCount++;
 if (readCount == 1) {
 wrt.acquire();
 }
 mutex.release();
 System.out.println("Thread "+Thread.currentThread().getName() + " is READING: " + message);
 Thread.sleep(1500);
 System.out.println("Thread "+Thread.currentThread().getName() + " has FINISHED READING");
 mutex.acquire();
 readCount--;
 if(readCount == 0) {
 wrt.release();
 }
 mutex.release();
 } catch (InterruptedException e) {
 System.out.println(e.getMessage());
 }
 }
 }
 static class Writer implements Runnable {
 public void run() {
 try {
 wrt.acquire();
 message = "Good Morning";
 System.out.println("Thread "+Thread.currentThread().getName() + " is WRITING: " + message);
 Thread.sleep(1500);
 System.out.println("Thread "+Thread.currentThread().getName() + " has finished WRITING");
 wrt.release();
 } catch (InterruptedException e) {
 System.out.println(e.getMessage());
 }
 }
 }

 public static void main(String[] args) {
 Reader read = new Reader();
 Writer write = new Writer();
 Thread r1 = new Thread(read);
 r1.setName("Reader1");
 Thread r2 = new Thread(read);
 r2.setName("Reader2");
 Thread r3 = new Thread(read);
 r3.setName("Reader3");
 Thread w1 = new Thread(write);
 w1.setName("Writer1");
 Thread w2 = new Thread(write);
 w2.setName("Writer2");
 Thread w3 = new Thread(write);
 w3.setName("Writer3");
 w1.start();
 r1.start();
 w2.start();
 r2.start();
 w3.start();
r3.start();
 }
}