// Define the bank

public class Bank {
  // Perform a transaction
  synchronized public void doTransaction(Transaction transaction) {
    int balance = transaction.getAccount().getBalance();               // Get current balance

    switch(transaction.getTransactionType()) {
      case CREDIT:
        // Credits require a lot of checks...
        try {
          Thread.sleep(100);

        } catch(InterruptedException e) {
          System.out.println(e);
        }
        balance += transaction.getAmount();                            // Increment the balance
        break;

      case DEBIT:
        // Debits require even more checks...
        try {
          Thread.sleep(150);

        } catch(InterruptedException e) {
          System.out.println(e);
        }
        balance -= transaction.getAmount();                            // Decrement the balance
        break;

      default:                                                         // We should never get here
        System.out.println("Invalid transaction");
        System.exit(1);
   }
    transaction.getAccount().setBalance(balance);                      // Restore the account balance
  }
}