打印菱形

import java.util.*;
public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            int n = sc.nextInt() + 1;
            StringBuilder sb = new StringBuilder();
            while(sb.length() < n - 1) sb.append(" ");
            sb.append("* ");
            int m = n;
            while(m-- > 1){    //打印正金字塔
                System.out.println(sb);
                sb.deleteCharAt(0);
                sb.append("* ");
            }
            sb = new StringBuilder();
            while(sb.length() < n*2) sb.append("* ");
            while(n-- > 0){    //打印倒金字塔
                System.out.println(sb);
                int len = sb.length();
                sb.delete(len - 2, len);
                sb.insert(0, " ");
            }
        }
    }
}