打印空心菱形

import java.util.Scanner;
class Test {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		System.out.println("请输入空心菱形行数（奇数）：");
		int num = sc.nextInt();
		if(num%2==0){
			System.out.println("请输入正奇数！");
			return;
		}
		char[][] arr = new char[num][num];
		int middle = (num/2);
		for (int i=0; i