Java - 将小时（双倍）转换为分钟（整数），反之亦然
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Java - Converting hours(in double) to minutes(integer) and vice versa
提问by uno
I need the correct formula that will convert hours to minutes and vice versa. I have written a code, but it doesn't seem to work as expected. For eg: If I have hours=8.16, then minutes should be 490, but I'm getting the result as 489.
我需要正确的公式来将小时转换为分钟，反之亦然。我写了一个代码，但它似乎没有按预期工作。例如：如果我有 hours=8.16，那么分钟应该是 490，但我得到的结果是 489。
import java.io.*;
class DoubleToInt {
public static void main(String[] args) throws IOException{
BufferedReader buff =
new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter the double hours:");
String d = buff.readLine();
double hours = Double.parseDouble(d);
int min = (int) ((double)hours * 60);
System.out.println("Minutes:=" + min);
}
}
回答by Bohemian
That's because casting to inttruncatesthe fractional part - it doesn't round it:
那是因为强制转换会int截断小数部分 - 它不会四舍五入：
8.16 * 60 = 489.6
When cast to int, it becomes 489.
当转换为 时int，它变为 489。
Consider using Math.round()for your calculations:
考虑使用Math.round()您的计算：
int min = (int) Math.round(hours * 60);
Note: doublehas limited accuracy and suffers from "small remainder error" issues, but using Math.round()will solve that problem nicely without having the hassle of dealing with BigDecimal(we aren't calculating inter-planetary rocket trajectories here).
注意：double精度有限并且存在“小余数误差”问题，但使用Math.round()将很好地解决该问题而无需处理BigDecimal（我们在这里不计算行星际火箭轨迹）。
FYI, to convert minutes to hours, use this:
仅供参考，要将分钟转换为小时，请使用以下命令：
double hours = min / 60d; // Note the "d"
You need the "d" after 60to make 60 a double, otherwise it's an intand your result would therefore be an inttoo, making hoursa whole number double. By making it a double, you make Java up-cast min to a double for the calculation, which is what you want.
你需要在“d”之后加上6060 a double，否则它是 an int，因此你的结果也会是 an int，使hours整数翻倍。通过将其设置为 a double，您可以将 Java 向上转换为 min 以进行计算，这正是您想要的。
回答by Ankit
8.16 X 60 comes out to be 489.6 and if you convert this value to int, you will get 489
8.16 X 60 结果是 489.6，如果你把这个值转换成 int，你会得到 489
int a = (int)489.6;
System.out.println("Minutes:=" + a);
