[问题]获取一个整数有多少位

swift 代码

func getDigits(with number: Int) -> Int {
    var digit = 1
    var num = number
    while num / 10 != 0 {
        num /= 10
        digit += 1
    }
    return digit
}
var stringTime: TimeInterval = 0
var digitTime: TimeInterval = 0
for _ in 0 ..< 10000000 {
    let num = Int(arc4random())
    do {
        let start = Date().timeIntervalSince1970
        let _ = String(num).count
        let end = Date().timeIntervalSince1970
        stringTime += (end - start)
    }
    do {
        let start = Date().timeIntervalSince1970
        let _ = getDigits(with: num)
        let end = Date().timeIntervalSince1970
        digitTime += (end - start)
    }
    
}
print("转换成字符串: \(stringTime)")
print("通过计算: \(digitTime)")

Java 代码

import java.util.Date;
import java.util.Random;

class Digit {
    public static void main(final String[] args) {
        Random r = new Random();

        long stringTime = 0;
        long digitTime = 0;

        for (int i = 0; i < 10000000; i++) {
            int number = r.nextInt(10);
            {
                long start = (new Date()).getTime();
                int count = ("" + number).length();
                long end = (new Date()).getTime();
                stringTime += (end - start);
            }
            {
                long start = (new Date()).getTime();
                int count = Digit.getDigits(number);
                long end = (new Date()).getTime();
                digitTime += (end - start);
            }
        }
        System.out.print("转换成字符串:"+ stringTime+"\n");
        System.out.print("通过计算:"+ digitTime+"\n");
    }

    static int getDigits(final int number) {
        int digit = 1;
        int num = number;

        while (num / 10 != 0) {
            num /= 10;
            digit += 1;
        }
        return digit;
    }
}

Swift 10次样本 单位：s

Java 10次样本 单位：ms

疑问：同样是很大的数字 Swift 的表现是转成字符串获取位数比直接计算的方式耗时少， 而在 java 中表现相反 并且 java 整体用时好像比 swift 要少 why？？？