Need help with Java Producer Consumer Problem, NullPointerException
- by absk
This is my code:
package test;
import java.util.logging.Level;
import java.util.logging.Logger;
class Data{
int ar[]=new int[50];
int ptr;
Data()
{
for(int i=0;i<50;i++)
ar[i]=0;
ptr=0;
}
public int produce()
{
if(this.ptr<50)
{
this.ar[this.ptr]=1;
this.ptr++;
return this.ptr;
}
else return -1;
}
public int consume()
{
if(this.ptr>0)
{
this.ar[this.ptr]=0;
this.ptr--;
return this.ptr;
}
else
return -1;
}
}
class Prod implements Runnable{
private Main m;
Prod(Main mm)
{
m=mm;
}
public void run()
{
int r = m.d.produce();
if (r != -1) {
System.out.println("Produced, total elements: " + r);
} else
{
try {
wait();
}
catch (InterruptedException ex) {
Logger.getLogger(Prod.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
class Cons implements Runnable{
private Main m;
Cons(Main mm)
{
m=mm;
}
public void run()
{
int r=m.d.consume();
if(r!=-1)
System.out.println("Consumed, total elements: " + r);
else
{
try {
wait();
}
catch (InterruptedException ex) {
Logger.getLogger(Prod.class.getName()).log(Level.SEVERE, null, ex);
}
}
notify();
}
}
public class Main{
Data d;
public static void main(String s[]) throws InterruptedException{
Main m = new Main();
Prod p = new Prod(m);
Cons c = new Cons(m);
new Thread(p).start();
new Thread(c).start();
}
}
It is giving following errors:
Exception in thread "Thread-0"
Exception in thread "Thread-1"
java.lang.NullPointerException
at test.Cons.run(Main.java:84)
at java.lang.Thread.run(Thread.java:619)
java.lang.NullPointerException
at test.Prod.run(Main.java:58)
at java.lang.Thread.run(Thread.java:619)
I am new to Java. Any help will be appreciated.
