Question

I played a bit with binary trees and built a menu which the user chooses whether to build a binary tree, insert a value to the binary tree he built or delete it, when I clicked on the creation of a tree. The tree is created, then the menu appeared again and now I want to put a number in this tree, but that variable is not set in the case, each case should set its variable ? Or you can use a global variable?
here its my code of the menu class.

import java.util.Comparator;
 import java.util.Scanner;


 public class TreeMenu {

 public static void main(String[] args) {

     while(true ){
         System.out.println("\n------------Menu-----------");
         System.out.println("1. Create Tree");
         System.out.println("2. Delete Tree");
         System.out.println("3. Insert Value INTO the tree");
         System.out.println("4. Exit ");
         System.out.println("Please Select Your Choice");

         Scanner choice = new Scanner(System.in); 
         int i = choice.nextInt();
         if(i>0 && i<=4){
         switch (i)
          {

            case 1:{

                System.out.println("Creating a Tree Please Wait........");
                Comparator comp = new IntegerComparator();
                BST tree1 = new BST(comp);
                break;
            }
            case 2:{
                System.out.println("You Chose TWO");
                break;
            }
            case 3:{
                Scanner Number = new Scanner(System.in); 
                 int num = Number.nextInt();
                 tree1.insert(num);

            }
            case 4:{
                System.exit(0);

            }

           }

          }
         else{
             System.out.println("There is no number in the menu like that "+i);
             System.exit(0); 

         }
     }

 }

 }

how i can use the same tree that created and insert into him values?
thanks

Answer 1

Declare tree1 as a private global variable as

  public class TreeMenu {
    private static BST tree1 = null;
    .....

Now instantiate that tree1 inside the switch case 1, then you can use the same tree variable inside case 2

A thing to note is you would need to do error checking in case 2 and 3, if tree1 == null, that would mean no tree has been created yet.