Thread: MuliThreading Unable to get outputs but many NPES.....

I have been trying for days and nights , no compile error , but alot of NPEs error .......

Please help !!! I am working very hard to solve this assignment.

Thank you so so much in advance.

This is my Test program

----------

import java.util.*;
 
public class Test
{
 
public static void main (String[]args)
{
int totalShares = 0 ;
double totalCost = 0.0;
double totalProfitLoss = 0.0; 
int rand1 = 0;
double rand2 = 0.0;
Stock stock = new Stock("FCS",totalShares,totalCost,totalProfitLoss);
 
BuyThread bt1 = new BuyThread (rand1 , rand2);
BuyThread bt2 = new BuyThread (rand1 , rand2);
SellThread st1 = new SellThread (rand1 , rand2);
SellThread st2 = new SellThread (rand1 , rand2);
bt1.start();
bt2.start();
st1.start();
st2.start();
 
try
{
System.out.println ("Tracking of stock:  " +stock.name);
bt1.join();
bt2.join();
st1.join();
st2.join();
 
System.out.println ("Total shares now " +stock.totalShares + " at total cost " +stock.totalCost );
System.out.println ("At$ 36.00 per share, profit is " + stock.getProfit(36.00));
}
catch (InterruptedException e)
{}
}
}

This is my Stock Class

----------

import java.util.*;
public class Stock
{
String name;
int totalShares;
double totalCost; 
double totalProfitLoss;
 
 
    public Stock(String name, int totalShares, double totalCost,double totalProfitLoss )
    {
        this.name = name;
        this.totalShares = totalShares;
        this.totalCost = totalCost;
        this.totalProfitLoss = totalProfitLoss;
    } 
 
    public String getName()
    {
        return name;
    }
    public double getTotalShares () 
    {
        totalShares++;
        return totalShares;
    }
    public double getTotalCost () 
    {
        totalCost++;
        return totalCost;
    }
    public double getTotalProfitLoss() 
    {
 
        return totalProfitLoss;
    }
 
    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 ;
}
 
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

----------

import java.util.*;
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

--- Update ---

No experts around at this hour?

Good Day , Sir ! Your help is greatly appriciated .

This is th output i got



Tracking of stock: FCS
Total shares now 0 at total cost 0.0
At$ 36.00 per share, profit is 0.0

----------------------------------------------------------------

Exception in thread "Thread-1" Exception in thread "Thread-2" java.lang.NullPointerException
at BuyThread.run(BuyThread.java:21)
java.lang.NullPointerException
at BuyThread.run(BuyThread.java:21)
Exception in thread "Thread-4" java.lang.NullPointerException
at SellThread.run(SellThread.java:22)
Exception in thread "Thread-3" java.lang.NullPointerException
at SellThread.run(SellThread.java:22)

Hi Sir, I dont know how to read....... Can you tell me which line have problems? Or which variables I point wrongly ?

Hi Sir, I wrote a Pool class to see what output I got.
Looks good
" 38 shares has been brought at $ 53.87
26 shares has been brought at $ 43.04 "

Now my problem is how do i call the buy method or sell method in my Stock Class ?
I assumed I that I wrote the wrong thing here
'stock.buy (rand1 , rand2);
System.out.println (rand1+" shares has been brought at $"+rand2) ;'

import java.util.*;
public class Pool
{
private int rand1 ;
private double rand2;
private Stock stock;
 
public Pool (int rand1,double rand2)
{
this.rand1 = rand1 ;
this.rand2 = rand2 ;
//this.stock = stock;
}
 
public static void main (String[]args)
{
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 ;
System.out.println (rand1+" shares has been brought at $ "+rand2) ;
//stock.sell (rand1 , rand2);
//System.out.println (rand1+"shares has been brought at $"+rand2) ;
 
try
{
Thread.sleep(60);
}
catch (InterruptedException e)
{}
}
}
}

But Still , i dont know why it show me NPEs on line 21 ...... I thought I did the correct way

Ok , now i got my output but , everything doesnt seem to be in order. I tried for days and nights. Now I understand more about Multi Threading. How do i get the output as what i expected ? Can someone advise me which part did I do wrongly ?

This is my Test program

----------

    import java.util.*;
 
    public class Test
    {
 
    public static void main (String[]args)
    {
    int totalShares = 0;
    double totalCost = 0.0;
    double totalProfitLoss = 0.0; 
    int rand1 = 0;
    double rand2 = 0.0;
    Stock stock = new Stock("FCS",totalShares,totalCost,totalProfitLoss);
 
    System.out.println ("Tracking of stock:  " +stock.name);
    BuyThread bt = new BuyThread (rand1 , rand2 , stock);
    SellThread st = new SellThread (rand1 , rand2 , stock);
    bt.start();
    st.start();
 
    try
    {
    bt.join();
    st.join();
 
 
    System.out.println ("At$ 36.00 per share, profit is " + stock.getProfit(36.00));
    }
    catch (InterruptedException e)
    {}
    }
    }

This is my Stock Class

----------

    import java.util.*;
    public class Stock
    {
    String name;
    int totalShares;
    double totalCost; 
    double totalProfitLoss;
 
 
    public Stock(String name, int totalShares, double totalCost,double totalProfitLoss )
    {
        this.name = name;
        this.totalShares = totalShares;
        this.totalCost = totalCost;
        this.totalProfitLoss = totalProfitLoss;
    } 
 
    public String getName()
    {
        return name;
    }
    public double getTotalShares () 
    {
        //totalShares++;
        return totalShares;
    }
    public double getTotalCost () 
    {
       // totalCost++;
        return totalCost;
    }
    public double getTotalProfitLoss() 
    {
 
        return totalProfitLoss;
    }
 
 
 
    public void buy(int shares, double pricePerShare)
    {
        totalShares += shares;
        totalCost += shares * pricePerShare;
        System.out.println ("Total shares now at " +totalShares+ " at total cost $ " +totalCost);
 
    }
 
    public boolean sell(int shares, double pricePerShare) 
    {
      double sellCost = shares * pricePerShare;
 
 
      if (shares >= totalShares || sellCost >= totalCost){
 
          return false;
 
        }
        else {
          totalShares -= shares;
          totalCost -= sellCost;
 
          System.out.println ("Total shares now at " +totalShares+ " at total cost $ "+totalCost);   
 
            return true;
 
        }
 
    }
 
    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 rand1 ;
    private double rand2;
    private Stock stock;
 
    public BuyThread (int rand1,double rand2,Stock stock)
    {
    this.rand1 = rand1 ;
    this.rand2 = rand2 ;
    this.stock = stock;
    }
 
    public void run()
    {
    for (int j = 0 ; j < 2; 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 (50);
    }
    catch (InterruptedException e)
    {}
    }
    }
    }

This is my SellThread

----------

    import java.util.*;
    public class SellThread extends Thread
    {
    private int rand1 ;
    private double rand2;
    private Stock stock;
 
    public SellThread (int rand1,double rand2,Stock stock)
    {
    this.rand1 = rand1 ;
    this.rand2 = rand2 ;
    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 sold at $"+rand2) ;
 
 
    try
    {
    Thread.sleep(30);
    }
    catch (InterruptedException e)
    {}
    }
    }
    }

I got this output

Tracking of stock: FCS
Sell Total shares now at 13 at total cost $ 381.0999999999997
Buy Total shares now at 50 at total cost $ 1664.9999999999998
37 shares has been sold at $34.7
50 shares has been brought at $33.3
32 shares has been sold at $51.97
Buy Total shares now at 18 at total cost $ 555.1499999999996
5 shares has been brought at $34.81
At$ 36.00 per share, profit is 92.85000000000036



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

Empty catch blocks are pointless, less than worthless. Put something in there to let you know when something has gone wrong and what it was.

Looking at your last "I am expecting" paragraph, why are you expecting that output? Can you trace why you expect that (or something like it) to happen? Or, you might attack it another way: Explain why the output you are getting is unreasonable or unexpected. First explain either or both approach to yourself, and then let us know what you discovered if you want help unraveling the mystery.

You say you're getting an error, so you know something's wrong with your code. What is the error? Please post it, copied and pasted into a post.