用Java编码归并排序， 利用归并排序算法将读入的n个数从小到大排序后输出。

好的，下面是Java代码实现归并排序并对n个数进行排序：

import java.util.Scanner;

public class MergeSort {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] arr = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i] = scanner.nextInt();
        }
        mergeSort(arr, 0, n - 1);
        for (int i = 0; i < n; i++) {
            System.out.print(arr[i] + " ");
        }
    }

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

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

代码中的mergeSort方法实现归并排序，merge方法实现归并操作。首先读入n个数，然后调用mergeSort方法进行排序，最后输出排好序的数组。