java 输出一个空心菱形

以下是 Java 代码实现空心菱形的输出：

import java.util.Scanner;

public class Diamond {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("请输入菱形的边长：");
        int n = input.nextInt();

        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= n - i; j++) {
                System.out.print(" ");
            }
            for (int k = 1; k <= 2 * i - 1; k++) {
                if (k == 1 || k == 2 * i - 1) {
                    System.out.print("*");
                } else {
                    System.out.print(" ");
                }
            }
            System.out.println();
        }

        for (int i = n - 1; i >= 1; i--) {
            for (int j = 1; j <= n - i; j++) {
                System.out.print(" ");
            }
            for (int k = 1; k <= 2 * i - 1; k++) {
                if (k == 1 || k == 2 * i - 1) {
                    System.out.print("*");
                } else {
                    System.out.print(" ");
                }
            }
            System.out.println();
        }
    }
}

输入菱形的边长后，程序会输出一个空心的菱形图形。