Java中使用Flag变量实现菜单跳转：原理与实践

import java.util.Scanner;

public class MenuNavigation {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        boolean backToMain = false; // 初始化flag变量

        while (true) {
            System.out.println("Main Menu:");
            System.out.println("1. Option A");
            System.out.println("2. Option B");
            System.out.println("3. Exit");

            System.out.print("Enter your choice: ");
            int choice = scanner.nextInt();
            scanner.nextLine(); // Consume newline

            switch (choice) {
                case 1:
                    System.out.println("You selected Option A.");
                    // Sub-menu for Option A
                    while(true){
                        System.out.println("Option A Sub-menu:");
                        System.out.println("1. Do something");
                        System.out.println("2. Back to Main Menu");
                        System.out.print("Enter your choice: ");
                        int subChoice = scanner.nextInt();
                        scanner.nextLine();

                        if(subChoice == 1){
                            System.out.println("Doing something...");
                        } else if (subChoice == 2){
                            backToMain = true; // 设置flag变量
                            break; // Exit sub-menu
                        } else {
                            System.out.println("Invalid choice. Please try again.");
                        }
                    }
                    if(backToMain){
                        backToMain = false; //reset flag
                        continue; // 返回主菜单
                    }
                    break;
                case 2:
                    System.out.println("You selected Option B.");
                    // Add logic for Option B here
                    break;
                case 3:
                    System.out.println("Exiting the program.");
                    scanner.close();
                    return;
                default:
                    System.out.println("Invalid choice. Please try again.");
            }
        }
    }
}