/* This class is not correct. It needs to be fixed to work in a
 * sequential setting, and also a multithreaded setting. What must we
 * do to change it? */

public class BankAccount {
    private static int totalTransfers = 0; // guarded by xferLock
    private static Object xferLock = new Object(); 
    private double balance; // guarded by this
    public BankAccount(double initialBalance) {
	this.balance = initialBalance;
    }
    synchronized public void withdraw(double amount) {
	balance -= amount;
    }
    synchronized public void deposit(double amount) {
	balance += amount;
    }
    /* synchronized */ public void transfer(double amount, BankAccount other) {
	// Uncommenting the above is redundant, and in fact can lead to deadlock!
	// In particular, if ba1 is one BankAccount and ba2 is another, than if one thread
	// does ba1.transfer(0.0,ba2) and another thread does ba2.transfer(0.0,ba1),
	// the two threads could deadlock
	this.withdraw(amount);
	other.deposit(amount);
	synchronized (xferLock) {
	    totalTransfers ++;
	}
    }
    synchronized public double getBalance() { return balance; }
    public static int getTotalTransfers() {
	synchronized (xferLock) {
	    return totalTransfers;
	}
    }
}