thread safety

class Test1
{

    public static void main(String args[])
    {
        Thread1 a=new Thread1(300);
        Thread2 b=new Thread2(200);

        Thread one=new Thread(a);
        Thread two=new Thread(b);
        try
        {
            one.start();
           two.start();
        one.join();
            two.join();
        }
        catch(InterruptedException e)
        {
        }
            //the parameters in the start method contains the amount to withdraw
    System.out.println(" The current balance is now = "+ Account.curr_bal);

    }


}


class Thread1 implements Runnable
{
    int withdrawal;
    Thread1(int amt)
    {
        withdrawal=amt;
    }

    public void run()
    {
      Account obj1=new Account();
      obj1.withdraw(withdrawal);
      System.out.println(" Withdrawal complete successfully done by Thread1");
          }
}

class Thread2 implements Runnable
{
    int withdrawal;
    Thread2(int amt)
    {
        withdrawal=amt;
    }

    public void run()
    {
        Account obj1=new Account();
        obj1.withdraw(withdrawal);
        System.out.println(" Withdrawal complete successfully done by Thread2");
        }
}

class Account
{
    static int curr_bal=400;
    void withdraw(int amt)
    {
        if(curr_bal>amt)
        {
            try
            {
                Thread.sleep(1000);
            }
            catch(InterruptedException e)
            {
            }
            curr_bal=curr_bal-amt;
        }
    }
}