Rewrite the class so that it throws appropriate exceptions instead of returning -1 as an error code. Write test code that attempts to withdraw and deposit invalid amounts and catches the exceptions that are thrown.

A method that returns a special error code can sometimes cause problems. The caller might ignore the error code or treat the error code as a valid return value. In this case it is better to throw an exception instead. The following class maintains an account balance and returns a special error code.
```
{
private double balance;
public Account()
{
balance = 0;
}
public Account(double initialDeposit)
{
balance = initialDeposit;
}
public double getBalance()
{
return balance;
}
// returns new balance or -1 if error
public double deposit(double amount)
{
if (amount > 0)
balance += amount;
else
return -1; // Code indicating error
return balance;
}
// returns new balance or -1 if invalid amount
public double withdraw(double amount)
{
if ((amount > balance) || (amount < 0))
return -1;
else
balance -= amount;
return balance;
}
}
```

This solution throws a NegativeAmount and InsufficientBalance exception. It is worth pointing out to the students the problems that would occur if negative account balances were desirable.

See the code in Account.java.