java使用递归实现三级菜单

javaCopy codeimport java.util.*;

public class Menu {
    
    private static Map<String, List<String>> menu = new HashMap<>();
    
    static {
        menu.put("A", Arrays.asList("A1", "A2", "A3"));
        menu.put("B", Arrays.asList("B1", "B2"));
        menu.put("C", Arrays.asList("C1"));
    }
    
    public static void main(String[] args) {
        printMenu();
    }
    
    private static void printMenu() {
        Scanner scanner = new Scanner(System.in);
        String input = "";
        while (!input.equals("exit")) {
            System.out.println("请选择一级菜单（输入字母 A/B/C）：");
            input = scanner.next().toUpperCase();
            if (!menu.containsKey(input)) {
                System.out.println("无效的输入，请重新输入！");
                continue;
            }
            List<String> subMenu = menu.get(input);
            printSubMenu(subMenu);
        }
    }
    
    private static void printSubMenu(List<String> subMenu) {
        Scanner scanner = new Scanner(System.in);
        String input = "";
        while (!input.equals("back")) {
            System.out.println("请选择二级菜单（输入数字 1/2/3）或返回上一级（输入 back）：");
            for (int i = 0; i < subMenu.size(); i++) {
                System.out.println((i+1) + ". " + subMenu.get(i));
            }
            input = scanner.next();
            if (!input.equals("back")) {
                int index = Integer.parseInt(input) - 1;
                if (index < 0 || index >= subMenu.size()) {
                    System.out.println("无效的输入，请重新输入！");
                    continue;
                }
                String item = subMenu.get(index);
                printSubSubMenu(item);
            }
        }
    }
    
    private static void printSubSubMenu(String item) {
        Scanner scanner = new Scanner(System.in);
        String input = "";
        while (!input.equals("back")) {
            System.out.println("请选择三级菜单（输入数字 1/2/3）或返回上一级（输入 back）：");
            System.out.println("1. " + item + " 1");
            System.out.println("2. " + item + " 2");
            System.out.println("3. " + item + " 3");
            input = scanner.next();
            if (!input.equals("back")) {
                int index = Integer.parseInt(input);
                if (index < 1 || index > 3) {
                    System.out.println("无效的输入，请重新输入！");
                    continue;
                }
                System.out.println("您选择了 " + item + " " + index);
            }
        }
    }
}