示例展示：Java实现归并排序算法及性能评估

public class MergeSort {
    public static void mergeSort(int[] arr) {
        if (arr == null || arr.length <= 1) {
            return;
        }
        int[] temp = new int[arr.length];
        mergeSort(arr, 0, arr.length - 1, temp);
    }

    private static void mergeSort(int[] arr, int left, int right, int[] temp) {
        if (left < right) {
            int mid = (left + right) / 2;
            mergeSort(arr, left, mid, temp);
            mergeSort(arr, mid + 1, right, temp);
            merge(arr, left, mid, right, temp);
        }
    }

    private static void merge(int[] arr, int left, int mid, int right, int[] temp) {
        int i = left;
        int j = mid + 1;
        int k = 0;
        while (i <= mid && j <= right) {
            if (arr[i] <= arr[j]) {
                temp[k++] = arr[i++];
            } else {
                temp[k++] = arr[j++];
            }
        }
        while (i <= mid) {
            temp[k++] = arr[i++];
        }
        while (j <= right) {
            temp[k++] = arr[j++];
        }
        for (i = 0; i < k; i++) {
            arr[left + i] = temp[i];
        }
    }
}

import java.util.Arrays;
import java.util.Random;

public class PerformanceTest {
    public static void main(String[] args) {
        int[] arr = generateRandomArray(1000000);
        System.out.println("排序前：" + Arrays.toString(arr));
        long startTime = System.currentTimeMillis();
        MergeSort.mergeSort(arr);
        long endTime = System.currentTimeMillis();
        System.out.println("排序后：" + Arrays.toString(arr));
        System.out.println("排序耗时：" + (endTime - startTime) + "毫秒");
    }

    private static int[] generateRandomArray(int length) {
        int[] arr = new int[length];
        Random random = new Random();
        for (int i = 0; i < length; i++) {
            arr[i] = random.nextInt(length);
        }
        return arr;
    }
}