Java:整数除法集合

Question

我正在编写一个程序，提示用户输入一家酒店的楼层总数、每一层的房间数以及被占用的房间数。最后要显示房间总数、占房间总数和占房间总数的百分比。我在显示被占房间的百分比方面有问题。我用了所有的整数。

这就是我所说的方程式：

roomsOccPercentage = (totalRoomsOccupied * 100) / totalRooms ;

当我将程序提交给我的教授的Java运行程序时，它会显示：

65 % of the Rooms are occupied.

但是我的教授提供的答案是66 %，所以程序不会接受我的文件。

有人知道我做错了什么吗？这是DecimalFormat错误吗？

编辑:这是整个代码

import java.util.Scanner; 
import java.text.DecimalFormat;

public class hw7_1 {
    public static void main(String[]args) {

        Scanner keyboard = new Scanner(System.in);
        DecimalFormat formatter = new DecimalFormat("#0");
        int totalFloors;
        int totalRooms = 0;
        int numFloors;
        int numRooms;
        int roomsOccupied;
        int totalRoomsOccupied = 0;
        int roomsOccPercentage = 0;

        //prompting users to input # of floors, no inputs below 1 floor
        do {
            System.out.println("Please enter the number of floors in the hotel: ");
            numFloors = keyboard.nextInt();

            if (numFloors < 1) {
                System.out.println("You have entered an invalid number of floors. ");
            }
        }
        while (numFloors < 1);

        //for loops on how many rooms on each hotel floors
        for ( int Floors = 1; Floors <= numFloors; Floors++) {
            if (Floors == 13 ) {
                continue;
            }

            do {
                System.out.println("Please enter the number of rooms on floor #: " + Floors );
                numRooms = keyboard.nextInt();

                if (numRooms < 10) {
                    System.out.println("You have entered an invalid number of rooms. ");
                }
            } while (numRooms < 10);

            System.out.println("Please enter the number of occupied rooms on floor #: " + Floors);
            roomsOccupied = keyboard.nextInt();

            totalRooms = totalRooms + numRooms;
            totalRoomsOccupied = totalRoomsOccupied + roomsOccupied;
            roomsOccPercentage = (totalRoomsOccupied * 100) / totalRooms ;
        }
        System.out.println("\nThe hotel has a total of " + totalRooms + " rooms.");
        System.out.println(totalRoomsOccupied + " of the rooms are occupied.");
        System.out.println(formatter.format(roomsOccPercentage) + "% of the rooms are occupied.");
    }
}

Answer 1

你需要先把你的roomsOccPercentage变成双倍。

double roomsOccPercentage = 0.0;

然后转换任一操作数，以避免整数除法。

roomsOccPercentage = (totalRoomsOccupied * 100.0) / totalRooms;

您可以使用显式强制转换(如(double)totalRoomsOccupied )，也可以将100设置为100.0 (浮点数)，从而使除法也成为浮点除法，而不是整数除法。

Answer 2

请注意，java使用自己的规则，您需要遵守它们。决定你是否想要结果的地板或细胞，遵循下面给出的例子。

double roomsOccPercentage;
roomsOccPercentage =Math.ceil((double)5/4); //will be 2
roomsOccPercentage =Math.ceil(5/4); //will be 1
roomsOccPercentage =Math.floor((double)5/4); //will be 1

我希望您现在可以找到java intresting。

Answer 3

如果你更喜欢进入双数来进行整数除法，那么你可以这样做。如果你不愿意，你不需要，这只是有点棘手：

private static int divideRoundUp(int denominator, int divisor) {
    return (denominator + divisor - 1) / divisor;
}

我们试试看：

    System.out.println(divideRoundUp(196, 3));
    System.out.println(divideRoundUp(197, 3));
    System.out.println(divideRoundUp(118, 2));
    System.out.println(divideRoundUp(119, 2));

这些指纹：

66
66
59
60

如果没有余数，如118 / 2所示，则得到正常结果。在其他情况下，结果被舍入。如何处理负分母和/或除数是留给读者的练习。

在学校里，我们中的许多人都知道，65.5或更高的数字应该被舍入到66，而在65.0和65.5之间的数字应该被四舍五入到65。如果您希望这样做，则方法有一点不同：

private static int divideRoundHalfUp(int denominator, int divisor) {
    return (denominator + divisor / 2) / divisor;
}

示范：

    System.out.println(divideRoundHalfUp(196, 3));
    System.out.println(divideRoundHalfUp(197, 3));
    System.out.println(divideRoundHalfUp(118, 2));
    System.out.println(divideRoundHalfUp(119, 2));

输出：

65
66
59
60