CashDispenser.java

// CashDispenser.java
// Represents the cash dispenser of the ATM

public class CashDispenser {
    // the default initial number of bills in the cash dispenser
    private final static int INITIAL_COUNT_100 = 500; // number of HKD 100 banknote
    private final static int INITIAL_COUNT_500 = 200; // number of HKD 500 banknote
    private final static int INITIAL_COUNT_1000 = 100; // number of HKD 1000 banknote

    private int count100; // number of HKD 100 banknote remaining
    private int count500; // number of HKD 500 banknote remaining
    private int count1000; // number of HKD 1000 banknote remaining

    // no-argument CashDispenser constructor initializes counts to default
    public CashDispenser() {
        count100 = INITIAL_COUNT_100; // set count for HKD 100 banknote to default
        count500 = INITIAL_COUNT_500; // set count for HKD 500 banknote to default
        count1000 = INITIAL_COUNT_1000; // set count for HKD 1000 banknote to default
    } // end CashDispenser constructor

    // simulates dispensing of specified amount of cash
    public void dispenseCash(int amount) {
        while (amount >= 1000 && count1000 > 0) {
            amount -= 1000;
            count1000--;
        }
        while (amount >= 500 && count500 > 0) {
            amount -= 500;
            count500--;
        }
        while (amount >= 100 && count100 > 0) {
            amount -= 100;
            count100--;
        }
    } // end method dispenseCash

    // indicates whether cash dispenser can dispense desired amount
    public boolean isSufficientCashAvailable(int amount) {
        int originalAmount = amount;

        // Check how many bills are needed
        int banknotesRequired1000 = amount / 1000;
        amount %= 1000;

        int banknotesRequired500 = amount / 500;
        amount %= 500;

        int banknotesRequired100 = amount / 100;

        // Check if we have enough bills of each denomination
        if (banknotesRequired1000 > count1000) {
            return false; // not enough HKD 1000 banknote
        }
        if (banknotesRequired500 > count500) {
            return false; // not enough HKD 500 banknote
        }
        if (banknotesRequired100 > count100) {
            return false; // not enough HKD 100 banknote
        }

        return true; // enough banknote available
    } // end method isSufficientCashAvailable
} // end class CashDispenser