Java 运费计算器

Question

我正在开发一个运费计算器，我已经把它全部写好了，但我有一个小问题。每 500 英里我需要收取 x 金额。它可以工作，但如果里程是 500 英里的倍数，则需要另外充电 500 英里。我明白为什么它会按照我写的方式这样做，但我不知道还有什么方法可以让行驶 750 英里的前 500 英里收取 2 次费用，然后其余的则收取 2 次费用。

public static void main(String[] args) {
    JOptionPane.showMessageDialog(null, "This program will ask you to enter the weight\n" +"of your package and how many miles it will travel.\n" +"It will then calculate the shipping cost for you.","Greeting",1);

    String weight = JOptionPane.showInputDialog(null, "Please enter the weight of your package in pounds such as 5.25.", "Weight", 1);
    Double weightnum = Double.parseDouble(weight);
    Double overweight = weightnum-10;

    String miles = JOptionPane.showInputDialog(null, "You have entered " +weightnum +" lbs.\n" +"Please enter in whole numbers how many miles your package needs to travel such as 250.", "Distance", 1);
    int milesnum = Integer.parseInt(miles);
    if (milesnum <500)
    {
        milesnum=0;
    }

    Double cost;
    if (weightnum < 2)
    {
        cost = (milesnum/500+1)*1.10;
    }
    else if (weightnum < 6)
    {
        cost = (milesnum/500+1)*2.50;
    }
    else if (weightnum < 10)
    {
        cost = (milesnum/500+1)*3.90;
    }
    else 
    {
        cost = (milesnum/500+1)*(4.00+(overweight*.5));
    }

    String strcost= String.format("%.2f", cost);

    JOptionPane.showMessageDialog(null, "It will cost $" +strcost +" to ship your " +weightnum +" lbs package " +miles +" miles.\n" +"Have a nice day!", "Cost", 1);
    System.exit(0);
}

}

Answer 1

使用Math.ceil :

Returns the smallest (closest to negative infinity) double value that is greater than or equal to the argument and is equal to a mathematical integer. Special cases:

• If the argument value is already equal to a mathematical integer, then the result is the same as the argument.

• If the argument is NaN or an infinity or positive zero or negative zero, then the result is the same as the argument.

• If the argument value is less than zero but greater than -1.0, then the result is negative zero.

cost = Math.ceil(milesnum/500.0)*multiplier;

表达式 milesnum/500.0 将返回 double 值(与 milesnum/500 不同，后者将返回 int)。然后，math.ceil 会将该值向上舍入。

如果 milesnum == 500，milesnum/500.0 为 1，四舍五入为 1。

如果 milesnum == 550，milesnum/500.0 为 1.1，四舍五入为 2。