java%E8%BE%93%E5%87%BA%E4%B8%80%E4%B8%AA%E7%A9%BA%E5%BF%83%E8%8F%B1%E5%BD%A2

要在Java中输出一个空心菱形，可以使用嵌套循环来实现。下面是一个示例代码：

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入菱形的行数：");
        int n = scanner.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();
        }
    }
}

这段代码会要求你输入菱形的行数，然后根据输入的行数打印出相应的空心菱形。