Java 强制用户在选项2之前选择选项1

我想强制用户在继续之前选择选项1，然后选择选项2。任何帮助都将不胜感激。 （注意，到目前为止，我只在java中完成了if、switch、while、for、do…while、方法和数组）

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在至少选择一次

1

之前，您无法显示选项

2

 Scanner sc = new Scanner(System.in);   

 int[] ages = new int[3];
 int choice;
 boolean is2Enabled=false,
 do{
   System.out.println("Average Age program");
   System.out.println("Enter 1 to enter ages");
   if(is2Enabled)
     System.out.println("Enter 2 to calculate the average Age");
   System.out.println("Enter 0 to Exit");
   choice=sc.nextInt();
   switch(choice)       
   {
       case 1:
       acceptAges(ages);
       is2Enabled=true;
       break;

       case 2:
       if(is2Enabled)
         averageAge(ages);
       else
         System.out.print("invalid option");
       break;

       default:
       System.out.print("invalid option");
    } 
  }while(choice != 0);
}

---

在至少选择一次

1

之前，您无法显示选项

2

 Scanner sc = new Scanner(System.in);   

 int[] ages = new int[3];
 int choice;
 boolean is2Enabled=false,
 do{
   System.out.println("Average Age program");
   System.out.println("Enter 1 to enter ages");
   if(is2Enabled)
     System.out.println("Enter 2 to calculate the average Age");
   System.out.println("Enter 0 to Exit");
   choice=sc.nextInt();
   switch(choice)       
   {
       case 1:
       acceptAges(ages);
       is2Enabled=true;
       break;

       case 2:
       if(is2Enabled)
         averageAge(ages);
       else
         System.out.print("invalid option");
       break;

       default:
       System.out.print("invalid option");
    } 
  }while(choice != 0);
}

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这是可能的，但我认为最好保持逻辑流这是可能的，但我认为最好保持逻辑流