// concurrent banking - base program for problem 2 of 1st assignment.

// simple class for bank account objects:
class account
{
    private double balance;  // account balance
    public account(double b) {balance=b;} // constructor sets initial balance

    public double inquiry() { return balance; } // balance inquiry
    public void deposit(double amt) 
    { if (amt>0) balance += amt; }
    public void withdraw(double amt)
    { if (amt<=balance) balance -= amt; 
	else System.out.println("not enough funds");
    }
}//account 


// Each owner of the account is represented by a thread:
class accountuser  // superclass for all account user threads
{ 
    protected account A;  // pointer to shared account
    public accountuser(account A) {this.A=A;}

    protected void printbalance()
    {
	System.out.printf("The balance is now %.2f\n", A.inquiry());
	System.out.flush(); // force immediate printing (dont' buffer)
    }

    protected void delay1sec() // simulated one second delay
    {
	try {Thread.sleep(1000);} catch(InterruptedException e){}
    }

}// accountuser superclass


// spender thread:
class spender extends accountuser implements Runnable
{
    int n; // controls length of loop
    public spender(account A, int m) { super(A); n=m; } // constructor
    
    public void run()
    {
	while (n-- > 0)
	    {
		double amount = Math.random()*1000; // spend up to $1000 
		amount = ((int)(amount*100+.5))/100.0; // round off to cents
		A.withdraw(amount); // love to spend!
	    }//while
	printbalance();
	
    }//run
       
}// spender


// earner thread:
class earner extends accountuser implements Runnable
{
    public earner(account A) { super(A); } // constructor
    
    public void run()
    {
	A.deposit(100);
	delay1sec();
	A.deposit(200);
	delay1sec();
	A.deposit(400);
	delay1sec();
	A.deposit(800);
	delay1sec();
	A.deposit(1600);  // the more I earn the more they spend ...
	printbalance();
    }//run
       
}// earner


// main thread for testing.
public class banking
{
    public static void main(String[] args) throws Exception
    {
	account checking = new account(100); // create account
	Thread earn = new Thread(new earner(checking));
	Thread spend = new Thread(new spender(checking,20));
	Thread spendmore = new Thread(new spender(checking,10));
	earn.start();
	spend.start();
	spendmore.start();
	earn.join();
	spend.join();  // spend.interrupt(); will interrupt waiting threads
	spendmore.join();
	System.exit(0);
    }// main
}