DecimalFormat部门

Question

double mny = 0;
mny = Double.parseDouble(JOptionPane.showInputDialog(null, "Enter the amount of Money", "Money Input", JOptionPane.QUESTION_MESSAGE));

//Check for Tens
System.out.println("The # of Tens is " + (int)(mny/10));
mny = mny%10;
System.out.println("The remaining amount of money is " + new DecimalFormat("0.00").format(mny) + " $ ");

//Check for Fives
System.out.println("The # of Fives is " + (int)(mny/5));
mny = mny%5;
System.out.println("The remaining amount of money is " + new DecimalFormat("0.00").format(mny) + " $ ");

//Check for Pennies
System.out.println("The # of Pennies is " + (int)(mny/0.01));
mny = mny%0.01;
System.out.println("The remaining amount of money is " + new DecimalFormat("0.00").format(mny) + " $ ");

如果我输入0.01，我会得到1便士，但如果我输入15.01，它会给我11015，但没有便士。

我该如何解决这个问题？

Answer 1

因为您将每次比较的结果赋给mny变量，所以尝试不使用它们：

double mny = 0;
mny = Double.parseDouble(JOptionPane.showInputDialog(null, "Enter the amount of Money", "Money Input", JOptionPane.QUESTION_MESSAGE));

//Check for Tens
System.out.println("The # of Tens is " + (int)(mny/10));
System.out.println("The remaining amount of money is " + new DecimalFormat("0.00").format(mny % 10) + " $ ");

//Check for Fives
System.out.println("The # of Fives is " + (int)(mny/5));
System.out.println("The remaining amount of money is " + new DecimalFormat("0.00").format(mny % 5) + " $ ");

//Check for Pennies
System.out.println("The # of Pennies is " + (int)(mny/0.01));
System.out.println("The remaining amount of money is " + new DecimalFormat("0.00").format(mny % 0.01) + " $ ");

Answer 2

您看到的问题是，为什么非常不鼓励使用double来表示货币价值。请改用BigDecimal。

public static void printCoins(double mny) {
    BigDecimal amount = BigDecimal.valueOf(mny);
    
    //Check for Tens
    BigDecimal[] quotientAndRemainder = amount.divideAndRemainder(BigDecimal.TEN);
    BigDecimal tens = quotientAndRemainder[0].setScale(0);
    amount = quotientAndRemainder[1];
    System.out.println("The # of Tens is " + tens);
    System.out.println("The remaining amount of money is " + amount.setScale(2, RoundingMode.HALF_EVEN) + " $ ");
    
    //Check for Fives
    quotientAndRemainder = amount.divideAndRemainder(BigDecimal.valueOf(5));
    BigDecimal fives = quotientAndRemainder[0].setScale(0);
    amount = quotientAndRemainder[1];
    System.out.println("The # of Fives is " + fives);
    System.out.println("The remaining amount of money is " + amount.setScale(2, RoundingMode.HALF_EVEN) + " $ ");
    
    //Check for Pennies
    quotientAndRemainder = amount.divideAndRemainder(BigDecimal.valueOf(0.01));
    BigDecimal pennies = quotientAndRemainder[0].setScale(0);
    amount = quotientAndRemainder[1];
    System.out.println("The # of Pennies is " + pennies);
    System.out.println("The remaining amount of money is " + amount.setScale(2, RoundingMode.HALF_EVEN) + " $ ");
}

测试

printCoins(0.01);

printCoins(15.01);

输出

The # of Tens is 0
The remaining amount of money is 0.01 $ 
The # of Fives is 0
The remaining amount of money is 0.01 $ 
The # of Pennies is 1
The remaining amount of money is 0.00 $ 

The # of Tens is 1
The remaining amount of money is 5.01 $ 
The # of Fives is 1
The remaining amount of money is 0.01 $ 
The # of Pennies is 1
The remaining amount of money is 0.00 $ 

Answer 3

您遇到的问题是浮点数表示不精确。

处理货币的最简单和最容易的方法是使用便士，它始终是一个整数，因此您可以使用int变量计算所有内容。

这就是银行处理购买交易数据的方式。

首先将用户输入转换为整数个便士：

double input = Double.parseDouble(JOptionPane.showInputDialog(null, "Enter the amount of Money", "Money Input", JOptionPane.QUESTION_MESSAGE));
int pennies = (int)(input * 100);

然后，您的代码的其余部分需要转换为使用便士，这很简单。