java：如何确认数组已在数组操作菜单中创建

Question

所以我正在制作这个数组操作菜单，但我的第一个选项是“创建数组”时遇到了问题。我应该在这里输入数组的大小，但如果它是 20，它会发送一条错误消息，我可以这样做。但是如果已经创建了一个数组，我也应该显示一条错误消息。我怎样才能做到这一点？感谢您的回复。

class process{
   Scanner in = new Scanner(System.in); 
   int choice1 =0;
   int limit1;
   int array[];
  
   public void m(){
    System.out.println("                   ARRAY OPERATION");
    System.out.println("                        menu");
    System.out.println("                 [1] Create Array");
    System.out.println("                 [2] Insert Element");
    System.out.println("                 [3] Search");
    System.out.println("                 [4] Display");
    System.out.println("                 [5] Delete");
    System.out.println("                 [0] Stop");
    System.out.print("                 Enter choice:");
     e();
  }
    
  public void e(){
    
    
     choice1 = in.nextInt();
     cls();
     
     switch(choice1){
      case 1:
       {
         
        System.out.println("Create Array");
        System.out.println("Enter the limit of your array: ");
        limit1 = in.nextInt();
        
        
        if(limit1 <5){
            System.out.println("Error: Minimum limit exceeded"); 
            System.out.println("Going back to main menu");
            m(); //loop to main menu
        }
        else if(limit1 >20){
            System.out.println("Error: Maximum limit exceeded");
            System.out.println("Going back to main menu");
            m(); //loop to main menu
        }
        else if(limit1 >=5 || limit1 <=20){
        System.out.println("An array with a limit of " + limit1 + " has been created");
        array = new int[limit1];
        m();
     }
     }

Answer 1

添加case 1:

   if (array != null) {
       System.out.println("Already exists");
       break;
   }