DaniWeb IT Discussion Community - Dining Philosophers Problem

can any one explain about the below code which is Dining Philosophers Problem..
//Dining Philosophers Problem

import java.util.Random;

class Monitor {

int phil_States[] = new int[5];   // 0=not_waiting, 1=waiting // 2=eating

boolean fork_States[] = new boolean[5];  // false = in use, true = free

Monitor() {        // constructor

   for(int i=0;i<5;i++) {

      phil_States[i]=0;

      fork_States[i]=true;

   }

}

synchronized void print_State()

{

System.out.println();        // newline

for(int i=0;i<5;i++)

     System.out.print(" " + phil_States[i]);        

}

synchronized void ask_to_eat(int pId)

{

   while(!fork_States[pId] || !fork_States[(pId+1)%4])

   {    // while it can't have both forks, wait

      phil_States[pId] = 1;  

      try 

  {wait();} 

  catch(InterruptedException e){} // it gets released

   }    // by a process doing a call to notify()

   phil_States[pId] = 2;  // eating

   fork_States[pId] = false;  // in use

   fork_States[(pId+1)%4] = false;

}

synchronized void ask_to_leave(int pId)

{

     fork_States[pId] = true; // available

     fork_States[(pId+1)%4] = true;

     phil_States[pId] = 0;  // thinking

     notify(); // free the Phil that has waited the longest

}

}

 

class Diners {

public static void main(String args[]) { // execution of the whole

   Monitor m = new Monitor(); // thing begins here

   Timer t = new Timer(m);  // make a new timer

   Phil p[] = new Phil[5];  // make an array of 5 refs to Phils

   for(int i=0; i<5; i++)

      p[i] = new Phil(i,m,t); // create the phils and start them

}

}

class Phil implements Runnable {

Monitor m;

Timer t;

Random r = new Random();  // Random number generator object

int pId;

float time;

Phil(int pId, Monitor m, Timer t) { // constructor

   System.out.println(pId + "is started: ");

   this.pId = pId;

   this.m = m;

   this.t = t;

   new Thread(this, "Phil").start(); // make a new thread and start it

}

public void run() {   // must override run, this is what

   for(int i=0; i<20; i++) {  // is executed when the thread starts

     m.ask_to_eat(pId);  // running

     time = 1000*r.nextFloat();

     try {Thread.sleep((int)time);} catch(Exception e){}

     m.ask_to_leave(pId);

     time = 1000*r.nextFloat();

     try {Thread.sleep((int)time);} catch(Exception e){}

   }

t.report_Stop();   // tell the timer this one is done

}       

}

class Timer implements Runnable {

Monitor m;

int completed;

Timer(Monitor m) {   // constructor

   this.m = m;

   new Thread(this, "Tim").start(); // make a new thread and start it

   completed=0;

}

public void report_Stop() {

   completed++;

}

public void run() {   // must override run(), this is 

   while(completed!=5) {  // what happens when the thread

      m.print_State();  // begins

      try {Thread.sleep(500);} catch(Exception e){}

   }

}

}