如果不使用 && 或 ||，我将如何编写这段代码？ 操作员？

Question

public static double calculateMinPayment(double newBalance) {
    double x;
    if (newBalance < 0.00) {
        return 0.00;
    } else if (newBalance > 0.00 && newBalance <= 49.99) {
        x = newBalance;
    } else if (newBalance >= 50.00 && newBalance <= 300) {
        x = 50.00;
    } else {
        x = newBalance * 0.2;
    }
    return x;     
}

I'm not able to use the operators && or ||, how would I be able to format this same code without those operators?

Answer 1

Since your conditions are in increasing size and with no gaps you don't need any AND conditions and the comparison can be made quite straight forward.

public static double calculateMinPayment(double newBalance) {
  double x;

  if (newBalance < 0.0) {
    return 0.0;
  } else if (newBalance < 50.0) {
    return newBalance;
  } else if (newBalance <= 300.0) {
    return 50.0;
  } else {
    return newBalance * 0.2;
  }
}

A small variation is to skip all the else since we are using return

if (newBalance < 0.0) {
  return 0.0;
} 
if (newBalance < 50.0) {
  return newBalance;
} 
if (newBalance <= 300.0) {
  return 50.0;
} 
return newBalance * 0.2;

Answer 2

You can use Nested if statements like below:

public static double calculateMinPayment(double newBalance) {
    double x;
    if (newBalance < 0.00) {
        return 0.00;
    } else if (newBalance > 0.00) {
        if (newBalance <= 49.99) {
            x = newBalance;
        } else if (newBalance >= 50.00) {
            if (newBalance <= 300) {
                x = 50.00;
            } else {
                x = newBalance * 0.2;
            }
        } else {
            x = newBalance * 0.2;
        }
    } else {
        x = newBalance * 0.2;
    }
    return x;
}

Answer 3

To avoid writing if totally, you could do the below. The LinkedHashMap keeps track of all conditions and the result to return if the condition is true . Since it is a LinkedHashMap the order of conditions evaluated is the order in which they are put in the map, similar to the order if you were to write if loops.

The logic returns the result of the first condition that evaluates to true

Any new condition can be simply added in the LinkedHashMap , at the position equivalent to the order in which you want it to be evaluated

private static double calculateMinPayment(final double newBalance) {
    LinkedHashMap<Predicate<Double>, Function<Double, Double>> conditionResult = new LinkedHashMap<>();
    conditionResult.put(balance -> balance < 0.0, balance -> 0.0);
    conditionResult.put(balance -> balance < 50.0, balance -> balance);
    conditionResult.put(balance -> balance < 300.0, balance -> 50.0);

    double minPayment = conditionResult.entrySet()
            .stream()
            .filter(entry -> entry.getKey().test(newBalance))
            .findFirst()
            .map(entry -> entry.getValue().apply(newBalance))
            .orElse(newBalance * 0.2);

    return minPayment;
}