我用 Golang 和 Java 测试了几个简单的函数。令我惊讶的是，Java 有时比 Golang 更快(尤其是在递归函数和标准库中的某些函数，如 math/rand.Rand)。我想知道为什么。这是我用于测试的一些代码和结果。

Golang 代码:

package main

import (
    "fmt"
    "math/rand"
    "time"
)

func calPi(pointCount int) float64 {
    inCircleCount := 0

    var x, y float64
    var Pi float64

    for i := 0; i < pointCount; i++ {
        x = rand.Float64()
        y = rand.Float64()

        if x*x+y*y < 1 {
            inCircleCount++
        }
    }

    Pi = (4.0 * float64(inCircleCount)) / float64(pointCount)

    return Pi
}

func fibonacci(c int64) int64 {
    if c < 2 {
        return c
    }

    return fibonacci(c-2) + fibonacci(c-1)
}

func main() {
    rand.Seed(time.Now().Unix()) 

    fmt.Printf("Test 1\n")

    startTime := time.Now()

    result := 0.0

    for i := 0.0; i < 1000000000; i = i + 1 {
        result += i * i
    }

    endTime := time.Now()

    fmt.Printf("Result: %v\n", result)

    fmt.Printf("Duration: %v\n", endTime.Sub(startTime))

    fmt.Printf("Test 2\n")

    startTime = time.Now()

    resultInt := fibonacci(50)

    endTime = time.Now()

    fmt.Printf("Result: %v\n", resultInt)

    fmt.Printf("Duration: %v\n", endTime.Sub(startTime))

    fmt.Printf("Test 3\n")

    startTime = time.Now()

    result = 0.0

    for i := 0.0; i < 100000000; i = i + 1 {
        result += rand.Float64()
    }

    endTime = time.Now()

    fmt.Printf("Result: %v\n", result)

    fmt.Printf("Duration: %v\n s", endTime.Sub(startTime))

    fmt.Printf("Test 4\n")

    startTime = time.Now()

    result = calPi(100000000)

    endTime = time.Now()

    fmt.Printf("Result: %v\n", result)

    fmt.Printf("Duration: %v s\n", endTime.Sub(startTime))

}

结果:

Test 1
Result: 3.333333328333552e+26
Duration: 1.449212507s
Test 2
Result: 12586269025
Duration: 1m31.645050682s
Test 3
Result: 4.999483069673434e+07
Duration: 2.534121566s
 sTest 4
Result: 3.14147056
Duration: 5.036491495s s

Java代码:

public class Performance {

    public static double calPi(int pointCount) {
        int inCircleCount = 0;

        double x, y;
        double Pi;

        for (int i = 0; i < pointCount; i++) {
            x = Math.random();
            y = Math.random();

            if (x * x + y * y < 1) {
                inCircleCount++;
            }
        }

        Pi = (4.0 * inCircleCount) / pointCount;

        return Pi;
    }

    public static double cal(double a, double b, double c) {
        return a * b / (c + 1) + a;
    }

    public static long fibonacci(long c) {
        if (c < 2)
            return c;
        return fibonacci(c - 2) + fibonacci(c - 1);
    }

    public static void main(String[] args) {

        System.out.println("Test 1");

        long startTime = System.currentTimeMillis();

        double result = 0.0;

        for (double i = 0.0; i < 1000000000; i = i + 1) {
            result += i * i;
        }

        long endTime = System.currentTimeMillis();

        float duration = (float) (endTime - startTime) / 1000;

        System.out.println("Result: " + result);
        System.out.println("Duration: " + duration + " s");

        System.out.println("Test 2");

        startTime = System.currentTimeMillis();

        long resultInt = fibonacci(50);

        endTime = System.currentTimeMillis();

        duration = (float) (endTime - startTime) / 1000;

        System.out.println("Result: " + resultInt);
        System.out.println("Duration: " + duration + " s");

        System.out.println("Test 3");

        startTime = System.currentTimeMillis();

        result = 0.0;

        for (double i = 0; i < 100000000; i = i + 1) {
            result += Math.random();
        }

        endTime = System.currentTimeMillis();

        duration = (float) (endTime - startTime) / 1000;

        System.out.println("Result: " + result);
        System.out.println("Duration: " + duration + " s");

        System.out.println("Test 4");

        startTime = System.currentTimeMillis();

        result = calPi(100000000);

        endTime = System.currentTimeMillis();

        duration = (float) (endTime - startTime) / 1000;

        System.out.println("Result: " + result);
        System.out.println("Duration: " + duration + " s");

    }
}

结果:

Test 1
Result: 3.333333328333552E26
Duration: 2.948 s
Test 2
Result: 12586269025
Duration: 60.816 s
Test 3
Result: 4.9999087237930864E7
Duration: 2.448 s
Test 4
Result: 3.14147284
Duration: 4.786 s

Test 2结果的差异着实让我震惊!请帮我找出原因，谢谢。如果有人可以给我示例来展示 Golang(与 Java)的优势，那就更好了。