AmountParses.java

    /**
     * Reads only valid amount from standard output and returns
     * it to the caller.
     *
     * @param prompt to be shown to the user to mark where to input
     * @param min amount allowed
     * @param max amount allowed
     * @return the valid amount
     */
    public BigDecimal inputBigDecimalValue(String prompt, BigDecimal min, BigDecimal max) {

        while (promptAndGetNextInput(prompt)) {
            String input = sc.nextLine();

            if (!isInputValid(input)) {
                System.out.println("Invalid input.");
                continue;
            }

            var amount = new BigDecimal(input);

            if (!isAmountInRange(amount, min, max)) {
                System.out.println("Input out of range from " + min + " to " + max);
                continue;
            }

            return amount;
        }

        return ZERO;
    }

    // The actual business logic of the parser
    private boolean isAmountInRange(BigDecimal amount, BigDecimal min, BigDecimal max) {
        return amount.compareTo(min) >= 0 && amount.compareTo(max) <= 0;
    }

    // Checks if the line input is valid or not
    private boolean isInputValid(String line) {
        try {
            new BigDecimal(line);
            return true;
        } catch (NumberFormatException nfe) {
            return false;
        }
    }

    // Convenience method to prompt before each new input
    private boolean promptAndGetNextInput(String prompt) {
        System.out.print(prompt);
        return sc.hasNext();
    }