JAVA算法题“打印图形”

题目：代码：

import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		if(n == 1)
			System.out.print('*');
		else if (n > 1 && n <= 20) {
			int i = 4 * n - 3;
			int j = 6 * n - 5;
			char arr[][] = new char[i][j];
			for(int a = 0; a < arr.length; a ++) {
				for(int b = 0; b < arr[1].length; b ++) {	
					if (a < n - 1) {
						arr[a][(3 * n - 3) - a] = '*';
						arr[a][(3 * n - 3) + a] = '*';
					}
					else if (a == n - 1 && b % 2 == 0)
						arr[a][b] = '*';
					else if (a > n - 1 && a <= 2 * n - 2) {
						arr[a][a - n + 1] = '*';
						arr[a][3 * n - 3 - a] = '*';
						arr[a][3 * n - 3 + a] = '*';
						arr[a][7 * n - 7 - a] = '*';	
					}		
					else if(a > 2 * n - 2)
						arr[a][b] = arr[4 * n - a - 4][b];
					else
						arr[a][b] = ' ';	
				}
			for (int k = 0; k < arr.length; k++) {
				for (int k2 = 0; k2 < arr[1].length; k2++)
					System.out.print(arr[k][k2]);
				System.out.println();
			}		
		}
	}
}