java - java中int到double的转换

Question

以下代码计算自动售货机分配的零钱。我的问题？我无法让更改变量工作，因为由于两种不同的数据类型(int 和 double 转换)，编译器不允许我工作。谁能帮我解决这个问题。我尝试过类型转换“change”，但它不会打印正确的数量。例如，如果变化是 0.25 美分，则变化值保持为零......当然原因显而易见。问题从第 16 行开始。我已将给出示例的部分注释为“change = 0.25”。

public String[] itemList = new String[] {"Water   ","Coke    ", "Diet Coke", "Iced Tea","Fanta   "};
public double[] priceList = new double[] {75,120, 120, 100, 150};
public int[] itemQty = new int[]{10,10,10,10,10};
public int[] coinList = new int[]{100,50,20,10,5};
public int[] coinQty = new int[]{10,10,10,10,10};
public double change;
public double paid;

    public void ReturnChange()
{
    int Denominations=5;
    int coins_dispensed = 0 ;
    int[] InitialArray = new int[Denominations];

    //My Problem begins here..for example if change is computed
      change = 0.25; //change is a global declaration of type double and carries values derived from different function
      int change1 = (int)change; //if i cast here, i get change as 0, thus the part that follows, fails to compute coins dispensed.

    for (int i=0; i < 5; i++)               
    {
    InitialArray[i] += coinQty[i];  // Copies Coin Quantity to Initial array for difference 

    }

    System.out.println("Your change is  "+NumberFormat.getCurrencyInstance().format(Math.abs(change1)) +" which comprises of:"); //OK till here


    for (int i=0; i<5; i++)
    {
        if (coinQty[i]>0) //if a particular denomination is available
        {
            coins_dispensed = (change1/coinList[i]); //dividing coins dispense with denomination
            coinQty[i] -= coins_dispensed; //reduce the quantity of the denomination dispensed
            change1 = change1 - (coinList[i] * coins_dispensed); //total the change
        }
        else                                            // Moves to next denomination if a particular coin runs out
        {
            coins_dispensed = (change1/coinList[i+1]);
            coinQty[i+1] -= coins_dispensed ;
            change1 = change1 - (coinList[i+1] * coins_dispensed);
        }
    }
    if (change1 != 0)                                   // In the case not enough coins to make change, selection is ignored. 
    {
        System.out.println("\n\n\t Sorry. The machine doesnt have enough coins to make up your change. Your last transaction has been ignored.");
    }
    else 
    {
        for (int i=0; i<Denominations; i++)
        {
            coins_dispensed = InitialArray[i] - coinQty[i];
            System.out.println( "\n\t\t\t" + coins_dispensed +" of "+ coinList[i] + "  cents coins");
        }
    }


}

Answer 1

您应该在任何地方使用整数，但以美分而不是美元来计算。打印时只需将数字除以 100 即可。

这是因为 float 和 double 无法准确表示用于货币的以10为基数的倍数，并且会引入舍入误差，特别是在相乘计算利率时。

参见Why not use Double or Float to represent currency?了解更多信息和讨论。