Payment Not Reset When No Change is Returned

[MudassarStd]

Affected Code Link

awesome-low-level-design/solutions/java/src/vendingmachine/ReturnChangeState.java

Lines 30 to 41 in 774631a

	@Override
	public void returnChange() {
	double change = vendingMachine.getTotalPayment() - vendingMachine.getSelectedProduct().getPrice();
	if (change > 0) {
	System.out.println("Change returned: $" + change);
	vendingMachine.resetPayment();
	} else {
	System.out.println("No change to return.");
	}
	vendingMachine.resetSelectedProduct();
	vendingMachine.setState(vendingMachine.getIdleState());
	}

Description
In the ReturnChangeState class, the returnChange method resets the payment only if there is a change to return. If no change is due, the payment remains unreset. This could lead to payment being carried over and added to subsequent transactions which is a critical issue here.

Expected Behavior
The payment should always be reset after the returnChange method is executed, regardless of whether there is any change to return or not.

Original Code

@Override
    public void returnChange() {
        double change = vendingMachine.getTotalPayment() - vendingMachine.getSelectedProduct().getPrice();
        if (change > 0) {
            System.out.println("Change returned: $" + change);
            vendingMachine.resetPayment();  // payment reset is conditional here
        } else {
            System.out.println("No change to return.");
        }
        vendingMachine.resetSelectedProduct();
        vendingMachine.setState(vendingMachine.getIdleState());
    }

Suggested Fix

@OverRide
public void returnChange() {
double change = vendingMachine.getTotalPayment() - vendingMachine.getSelectedProduct().getPrice();
if (change > 0) {
System.out.println("Change returned: $" + change);
} else {
System.out.println("No change to return.");
}

    vendingMachine.resetPayment();  // payment reset is unconditional
    vendingMachine.resetSelectedProduct();
    vendingMachine.setState(vendingMachine.getIdleState());
}