如何在整数除法和int结果在Java？ [英] How to round up integer division and have int result in Java?

问题描述

我刚刚写了一个微小的方法来计算手机短信的页数。我没有选择使用 Math.ceil ，实际上它看起来非常难看。

<这是我的代码：

  public class Main {
 
 / ** 
 * @param args命令行参数
 * / 
 public static void main（String [] args）{
 String message =今天我们偶然发现了一个巨大的性能泄漏，同时优化了光线投射算法令我们惊讶的是，Math.floor（）方法花费了将近一半的计算时间：三层操作的时间与一个三线性插值的时间相同，因为我们不能相信地板方法能够产生如此丰满的效果开销，我们写了一个小的测试程序，重现; 
 
 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）; 
 
 
 
 code 
 $ b我不太喜欢这段代码，我正在寻找一个更优雅的方式来做到这一点。有了这个，我期待3而不是3.0000000。任何想法？
 
解决方案
若要收集整数除法，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）; 
 
 $ / code $ / pre 
 
如果两个数字都是正数
 
 
  public static long roundUp（long num，long divisor）{
 return（num + divisor  -  1）/ divisor; 
} 
  
 
I just wrote a tiny method to count the number of pages for cell phone SMS. I didn't have the option to round up using Math.ceil, and honestly it seems to be very ugly.

Here is my code:
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);
        }
    }
}
I don't really like this piece of code and I'm looking for a more elegant way of doing this. With this, I'm expecting 3 and not 3.0000000. Any ideas?
解决方案
To round up an integer division you can use
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);
}
or if both numbers are positive
public static long roundUp(long num, long divisor) {
    return (num + divisor - 1) / divisor;
}


                        
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