Java long 除以 long 返回 0
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Dividing long by long returns 0
提问by user1815823
I am trying to calculate % of used diskspace in Windows and totaldrive denotes total diskspace of c drive in Long and freedrive dentoes free space in Long.
我正在尝试计算 Windows 中已用磁盘空间的百分比，totaldrive 表示 Long 中 c 驱动器的总磁盘空间，而 freedrive 表示 Long 中的可用空间。
long totaloccupied = totaldrive - freedrive;
Here calculating % of usage
这里计算使用百分比
Long Percentageused =(totaloccupied/totaldrive*100);
System.out.println(Percentageused);
The print statement returns 0. Can someone help as I am not getting the desired value
打印语句返回 0。有人可以帮忙，因为我没有得到所需的值
采纳答案by Lake
You are probably dividing a long with a long, which refers to (long/long = long) operation, giving a long result (in your case 0).
您可能正在将 long 与 long 相除，它指的是 (long/long = long) 操作，给出一个 long 结果（在您的情况下为 0）。
You can achieve the same thing by casting either operand of the division to a float type.
您可以通过将除法的任一操作数转换为浮点类型来实现相同的目的。
Long Percentageused = (long)((float)totaloccupied/totaldrive*100);
回答by Jason C
That will be evaluated left to right, the first integer division will return 0 (e.g. 8/10 evaluates to 0). Either convert values to floats or do 100*a/b. Floats will give you a more precise result.
这将从左到右计算，第一个整数除法将返回 0（例如 8/10 计算为 0）。将值转换为浮点数或执行 100*a/b。Floats 会给你一个更精确的结果。
回答by gdiazc
You are doing integer division! Since totaloccupiedis smaller than totaldrive, the division of both gives the answer 0. You should convert to double first:
你在做整数除法！既然totaloccupied小于totaldrive，两者的除法给出了答案0。您应该先转换为双精度：
double percentageUsed = 100.0 * totalOccupied / totalDrive;
Note that adding the decimal point to the 100ensures it is treated as a double.
请注意，将小数点添加到100确保它被视为double.
