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hi,
i have just started learning java threads. i have been given the task of solving dinning philosopher's problem by using only wait() and notify() methods. i cant use semaphores or monitors.
i have created philosophers as 5(0-4) threads and forks as objects upon which wait() and notify() methods can b called. i have writetn the code which i m posting 4 ur kind consideraton. my problem is that 0,2 and 4 philosophers are switching forks among them and the remaining 2 threads(1,3) are suffering 4m starvation. i dont know y?????
can anyone plz tell me that what i m doing wrong in this code and how its solution can be developed such that there is no deadlock,starvation or livelock.
plz plz plz help me.....
P.java(Philosopher's class)
public class P implements Runnable
{
String n;
F f1,f2;
Thread t;
int s=0;
int r=0;
public P(F ff1,F ff2,String name)
{
n=name;
f1=ff1;
f2=ff2;
t=new Thread(this,n);
t.start();
}
public void run()
{
for(int i=0;i<4;i++)
{
r=f1.get(); // get 1st fork
if(r==5) // if 1st fork has been acquired, then request 2nd one
s=f2.get();
f1.eat(n);
f1.left(n,f2); // place tae 2 forks back on table
try
{Thread.sleep(50);}
catch(Exception e)
{System.out.println(e);}
}// end for
}// end run
}
T.java(Main class)
public class T
{
public static void main(String args[])
{
F f[]=new F[5];
P p[]=new P[5];
for(int i=0;i<5;i++)
{
f[i]=new F();
}// end for
for(int i=0;i<5;i++)
{
String name="Philosopher # "+i;
if(i==0)
{p[0]=new P(f[4],f[i],name);} // sharing 2 fork objects with every philosopher
else
{p[i]=new P(f[i-1],f[i],name);}
}
}// end main
}//end class
F.java(Forks class)
public class F
{
private int fs=1; //represents availablity of forks
//if fs=1 -----> fork is available
//if fs=-1 -----> fork is not available
public F() //constructor
{
fs=1; // making all forks available at start of the program
}
public synchronized int get()
{
while(fs==-1)
{
try{wait();}
catch(Exception e)
{System.out.println(e);}
}//end while
fs=-1;
notifyAll();
return(5);
}// end get
public synchronized void eat(String h)
{
System.out.println(h+" is eating...");
try{Thread.sleep(1300);}
catch(Exception e)
{System.out.println(e);}
}// end eat
public synchronized void left(String h,F f2)
{
System.out.println(h+ " has finished eating ....");
this.fs=1;
notifyAll();
f2.fs=1;
notifyAll();
}// end left
}
