如何实现java Mergesort程序的基准测试？

Question

我想实现一个基准测试方法MergeSort和它的性能来衡量。我已经尝试用随机数填充要合并的数组，但是当代码运行时，数组会打印相同的随机数10次。这是为什么？
PS。我不能发布我编写的整个程序。Stackoverflow说代码太多了。

    public static void main(String[] args)
    {
        int arraySize = 10;
        int[] a = new int[arraySize];
        int k = 1000;
        int m = 1000;
        Random rnd = new Random();

        for (int j = 0; j < k; j++)
        {
            // fill the arraySize array with random numbers 
            for (int i = 0; i < 10*m; i++)
            {
                Arrays.fill(a, rnd.nextInt());
            }
        }

        long startTime = System.nanoTime();
        // array with predefined numbers and size
        //int[] a = { 11, 30, 24, 7, 31, 16, 39, 41 };
        int n = a.length;
        MergeSort m1 = new MergeSort();
        System.out.println("\nBefore sorting array elements are: ");
        m1.printArray(a, n);
        m1.mergeSort(a, 0, n - 1);

        long endTime = System.nanoTime();
        long timeElapsed = endTime - startTime;

        System.out.println("\n\nExecution time in nanoseconds: " + timeElapsed);
        System.out.println("Execution time in milliseconds: " + timeElapsed / 1000000);

        System.out.println("\nAfter sorting array elements are:");
        m1.printArray(a, n);
    }
}

Answer 1

for (int i = 0; i < 10*m; i++){
  Arrays.fill(a, rnd.nextInt());
}

这个循环用一个数填充数组10*m次。这就是为什么整个数组都有相同的数字。

解决方案：

int arraySize = 10;
int[] a = new int[arraySize];
for (int i = 0; i < arraySize; i++)
  a[i] = rnd.nextInt(1000);
System.out.println(Arrays.toString(a));