变化计算器减一

Question

我的Java计算器不会输出正确的更改量。它减一分钱，我不知道为什么。

我最初声明的变化作为单独的变量，但我然后只是乘以100的用户输入，但我仍然有同样的问题。

//this is where the variables are declared
double penny = 0.01;
double nickel = 0.05;
double dime = 0.10;
double quarter = 0.25;
double half_dollar = 0.50;
double dollar_coin = 1.00;

double user_input = 0;

int total_penny, total_nickel, total_dime, total_quarter, 
total_half_dollar, total_dollar_coin;

Scanner in = new Scanner (System.in);

//this is where the user can input data
System.out.println("What amount would you like change for: ");
user_input = in.nextDouble();

//this is where the users data will be processed
total_dollar_coin = (int) (user_input / 1.0);
user_input = user_input % 1.00;
total_half_dollar = (int) (user_input / 0.50);
user_input = user_input % 0.50;
total_quarter = (int) (user_input / 0.25);
user_input = user_input % 0.25;
total_dime = (int) (user_input / 0.10);
user_input = user_input % 0.10;
total_nickel = (int) (user_input / 0.05);
user_input = user_input % 0.01;
total_penny = (int) (user_input / 0.01);

//this is where the information will be outputted to the user
System.out.println("Your change will be: " + total_dollar_coin + " dollar 
coin(s) ");
System.out.println(total_half_dollar + " half dollar coin(s) " + 
total_quarter 
+ " quarter(s) ");
System.out.print(total_dime + " dime(s) " + total_nickel + " nickel(s) " + 
total_penny + " penny (or pennies) ");
    }

}

Answer 1

如果您调试这一点，你会看到，例如51.43最后一行：

total_penny = (int) (user_input / 0.01);

结果类似：

由于您强制转换为 int ，这将导致“意外输出”，在这种情况下为零（0）-请参阅上面第二条评论中有关以下内容的链接准确性。 尽管如此，解决该问题（作为一项教育活动）的可能方法是执行以下操作：

BigDecimal total_penny;
int total_nickel, total_dime, total_quarter, total_half_dollar, total_dollar_coin;

然后在您的total_penny行中：

user_input = user_input % 0.05;    --> you have 0.01 typo here
total_penny = BigDecimal.valueOf(user_input / 0.01);

格式化total_penny输出并输出：

String penny = NumberFormat.getInstance().format(total_penny);
System.out.println("..." + penny + " penny (or pennies) ");

这会给你你所期望的量：