Thread Synchronization

Synchronization, Producer and Consumer Problem, wait(), notify() methods of the Thread

class Controller
{
  private int counter;

  public void set(int i)
  {
      counter=i;
  }

  public int get()
  {
    return counter;
  }
}

class Producer extends Thread
{
  private Controller obj;

 public Producer(Controller c)
 {
  Obj=c;
 }

public void run()
{
 for(int i=0;I<5;i++ )
 {
   obj.set(i);
   System.out.println("put:"+j);
 }
}
}

class Consumer extends Thread
{
  private  Controller obj;

  public Consumer(Controller c)
  {
    obj=c;
  }

  public void run()
  {
    for(int  i=0;i<5;i++)
    {
        System.out.println("get:"+obj.get());
     }
  }
}

class TestSynchronization
{
 public  static void main(String args[])
 {
   Controller ctrl=new Controller;
   Producer thread1=new producer(ctrl);
   Consumer thread2=new Consumer(ctrl);
   thread1.start();
   thread2.start();
  }
}

O/P:-

put:0
get:0
get:0
get:0
get:0
get:0
put:1
put:2
put:3
put:4

Explanation:

In above program the producer creates value faster or slower than consumer that means there is no synchronization & this problem is known as producer_consumer problem.

Solution Of Producer & Customer Problem:-

Synchronized:

The synchronized block or synchronized method, allow only one thread at a time to execute.

Wait():

This method will cause the current thread to go into wait state until & unless notify() or notifyAll() is not called.

notifyAll():

It will give signal to all the threads which are in state to continue.

class Controller
{
  private int counter;
  private Boolean available=false;
  public synchronized int get()
  {
      while(available==false)
     {
      try
        {
          wait();
        }
        catch(Exception e)
        {
        }
     }
     notifyAll();
    available=false;
    return counter;
  }

 public synchronized int set(int value)
 {
   while(available==true)
   {
     try
     {
        wait();
     }
     catch(Exception e)
     {
     }
     counter=value;
     available=false;
     notifyAll();
    }
  }
}

class Producer extends Thread
{
  private Controller obj;
  public Producer(Controller c)
  {
   Obj=c;
  }

  public void run()
  {
   for(int i=0;I<5;i++ )
   {
     obj.set(i);
     System.out.println("put:"+j);
   }
 }
}

class Consumer extends Thread
{
 private  Controller obj;
 public Consumer(Controller c)
 {
  obj=c;
 }
 public void run()
 {
  for(int  i=0;i<5;i++)
  {
     System.out.println("get:"+obj.get());
  }
 }
}

class TestSynchronization
 {
  public  static void main(String args[])
  {
     Controller ctrl=new Controller;
     Producer thread1=new producer(ctrl);
     Consumer thread2=new Consumer(ctrl);
     thread1.start();
     thread2.start();
   }
}

O/P:
put:0
get:0
put:1
get:1
put:2
get:2
put:3
get:3
put:4
get:4