如何在Java中舍入整数除法并得到int结果？

Question

我只是写了一个小方法来计算手机短信的页数.我没有选择使用Math.ceil,老实说它似乎非常难看.

这是我的代码:

public class Main {

/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
   String message = "today we stumbled upon a huge performance leak while optimizing a raycasting algorithm. Much to our surprise, the Math.floor() method took almost half of the calculation time: 3 floor operations took the same amount of time as one trilinear interpolation. Since we could not belive that the floor-method could produce such a enourmous overhead, we wrote a small test program that reproduce";

   System.out.printf("COunt is %d ",(int)messagePageCount(message));



}

public static double messagePageCount(String message){
    if(message.trim().isEmpty() || message.trim().length() == 0){
        return 0;
    } else{
        if(message.length() <= 160){
            return 1;
        } else {
            return Math.ceil((double)message.length()/153);
        }
    }
}

我真的不喜欢这段代码,我正在寻找一种更优雅的方式.有了这个,我期待3而不是3.0000000.有任何想法吗？

Answer 1

使用Math.ceil()并将结果转换为int:

• 这仍然比使用abs()避免双倍更快.
• 使用底片时结果是正确的,因为-0.999将向上舍入为0

例:

(int) Math.ceil((double)divident / divisor);

Answer 2

要整数整数除法,您可以使用

import static java.lang.Math.abs;

public static long roundUp(long num, long divisor) {
    int sign = (num > 0 ? 1 : -1) * (divisor > 0 ? 1 : -1);
    return sign * (abs(num) + abs(divisor) - 1) / abs(divisor);
}

或两个数字都是正数

public static long roundUp(long num, long divisor) {
    return (num + divisor - 1) / divisor;
}

Answer 3

另一个不太复杂的单线程:

private int countNumberOfPages(int numberOfObjects, int pageSize) {
    return numberOfObjects / pageSize + (numberOfObjects % pageSize == 0 ? 0 : 1);
}

可以使用long而不是int; 只需更改参数类型和返回类型.

Answer 4

Google的Guava库在IntMath类中处理这个问题:

IntMath.divide(numerator, divisor, RoundingMode.CEILING);

与此处的许多答案不同,它处理负数.当尝试除以零时,它也会抛出适当的异常.

Answer 5

(message.length() + 152) / 153

这将给出一个"向上舍入"的整数.

Answer 6

long numberOfPages = new BigDecimal(resultsSize).divide(new BigDecimal(pageSize), RoundingMode.UP).longValue();