在Java中從int轉換為double

Question

以下代碼計算自動售貨機分配的零錢。 我的問題？ 由於兩種不同的數據類型（整數和雙精度轉換），編譯器不允許我使用更改變量，因此無法正常工作。 誰能幫我解決這個問題。 我已經嘗試過投放“更改”，但隨后無法打印正確的金額。 例如，如果找零是0.25美分，則找零值當然會保持零。 問題開始於第16行。我已將示例給出的部分注釋為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

您應該在各處使用integers ，但要以美分而非美元為單位。 打印時，只需將數字除以100。

這是因為floats和doubles數不能准確表示用於貨幣的基數10的倍數，並且會引入舍入誤差，尤其是在乘以例如計算利率時。

請參閱為什么不使用Double或Float表示貨幣？ 有關更多信息和討論。

Answer 2

看來您的所有變量都以美分持有價格（我想可樂不是120美元）。 但是您的找零顯然用美元指定。 因此，您可以做的是將更改乘以100，然后將其強制轉換為int 。

像那樣：

int change1 = (int) (change * 100); // convert dollars to cents and cast to int

如果在某個時候需要以美元（而不是美分）輸出change1，則必須將其轉換回：

float result = change1 / 100.0f;