Thread: Java MutiThreading Stock

I am doing a multi threading program . I am unable to get the output i want. I have no compilation error . But I cant get the result I , Null exception. Can someone please advise me ?

This is my Test program

----------

import java.util.*;
 
public class Test
{
 
 
public static void main (String[]args)
{
int totalShares = 0 ;
double totalCost = 0.0;
String name = "FCS";
double profit = 0.0;
int rand1 = 0;
double rand2 = 0.0;
Stock stock ;
double getprofit = 0.0 ;
double currentPrice = 36.00 ;
Thread bt[] = new Thread [2];
Thread st[] = new Thread [2];
//Stock stock = new Stock();
 
for (int i=0; i < 2; i ++)
{
bt[i] = new BuyThread (rand1, rand2);
bt[i].start() ;
}
 
for (int i=0; i < 2; i ++)
{
st[i] = new SellThread (rand1, rand2);
st[i].start() ;
}
 
for (int i=0; i < 2; i ++)
{
try
{
st[i].join();
bt[i].join();
}
catch (InterruptedException e)
{}
}
 
System.out.println ("Total shares now " +totalShares + " at total cost" +totalCost ); 
System.out.printf ("At$ 36.00 per share, profit is " +Stock.getprofit);
}
}

This is my Stock Class

----------

import java.util.*;
public class Stock
{
   String name;
   int totalShares;
   double totalCost;
   double totalProfitLoss;
 
 
    public Stock(String stockName)
    {
        name = stockName;
        totalShares = 0;
        totalCost = 0.00;
        totalProfitLoss = 0.00;
    } 
 
    public String getName()
    {
        return name;
    }
    public double getTotalShares () 
    {
        return totalShares;
    }
    public double getTotalCost () 
    {
        return totalCost;
    }
 
    public void buy(int shares, double pricePerShare)
    {
        totalShares += shares;
        totalCost += shares * pricePerShare;
    }
 
    public boolean sell(int shares, double pricePerShare) 
    {
      double sellCost = shares * pricePerShare;
 
      if (shares <= totalShares && sellCost <= totalCost){
          totalShares -= shares;
          totalCost -= sellCost;
          return true;
        }
        else {
            return false;
        }
    }
 
    public double getProfit (double currentPrice)
    {
        totalProfitLoss = currentPrice * totalShares;
        return totalProfitLoss - totalCost;
    }
}

This is my BuyThread program


----------

 
import java.util.*;
public class BuyThread extends Thread
{
private int share ;
private double cost;
private Stock stock;
 
public BuyThread (int share,double cost)
{
this.share = share ;
this.cost = cost ;
//this.stock = stock;
}
 
public void run()
{
for (int j = 0 ; j < 5; j++)
{
Random randShare = new Random ();
int rand1 = randShare.nextInt (50) + 5 ;
double rand2 = (int) ((Math.random() * 10 + 32)* 100.0)/100.0 ;
stock.buy (rand1 , rand2);
System.out.println (rand1+" shares has been brought at $"+rand2) ;
try
{ sleep (100);
}
catch (InterruptedException e)
{}
}
}
}

This is my SellThread

----------

 
public class SellThread extends Thread
{
private int share ;
private double cost;
private Stock stock;
 
public SellThread (int share,double cost)
{
this.share = share ;
this.cost = cost ;
//this.stock = stock;
}
 
public void run()
{
for (int j = 0 ; j < 2; j++)
{
Random randShare = new Random ();
int rand1 = randShare.nextInt (20) + 20 ;
double rand2 = (int) ((Math.random() * 32 + 23)* 100.0)/100.0 ;
stock.sell (rand1 , rand2);
System.out.println (rand1+"shares has been brought at $"+rand2) ;
 
try
{
Thread.sleep(60);
}
catch (InterruptedException e)
{}
}
}
}

I am expecting a output like this (Which I have error running:

Tracking of Stock : FCS
8 shares has been brought at $37.61
Total shares now 8 at total cost $300.88
33 shares has been brought at $36.31
Total shares now 41 at total cost $1499.11
17 shares has been sold at $42.67
Total shares now 24 at total cost $773.72
19 shares has been sold at $32.31
Total shares now 5 at total cost $159.83
31 shares has been brought at $33.85
Total shares now 36 at total cost $1209.18
28 shares has been brought at $36.37
Total shares now 64 at total cost $2227.54
20 shares has been brought at $35.49
Total shares now 84 at total cost $2937.34
At $36.00 per share, profit is $86.66

Welcome to the forum! Please read this topic to learn how to post code in code or highlight tags and other useful info for newcomers.

Too much unformatted code. Please correct according to the instructions in the link I provided, and then add a new post to let us know. Thanks.

Thank you. Is this the correct now?

Better. The code you posted does not compile due to this line:

System.out.printf ( "At$ 36.00 per share, profit is " + Stock.getprofit );

What should it be?

Edit: And if I delete that line, then there are 3 or 4 other NPEs later in the code. Please correct and give us code we can use to duplicate the error you want help with.

Further, if you're expecting to be able to predict the order in which the threads will execute and produce results, your expectations are not consistent with Java design.

Did I do my buyThread and sellThread correctly? I know that my Test class is done wrongly.

you are calling the methods on "stock" but it is not refrencing to any object.
whenever you need to call a method you hav to first create an object and give the refrence to it.
Stock stock;
stock.doSomething();
is worng.
Stock stock =new Stock(); // refrence to stock object
and then u call methods the refrence variable
stock.doSomething