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FolderTree In Java

Introduction 

 
Refer to the 'FolderTree.rar' in the 'Download Files' section above for the code.
 
In this blog, I will demonstrate Java code to print the folder tree or folder hierarchy or what you can call a directory structure.  
 
I have used class objects array as a data structure to store the information regarding the folders. An Array List of integers is used to store visited indexes and a variable named ‘tab’ to give tab spaces.
 
The Flow is basically like this:
  • First, it asks to enter the number of folders and we enter the number of folders.
  • For each folder, we enter Folder ID, folder’s Parent ID and Folder name.
  • After entering these details for each folder, the folder hierarchy gets displayed.
I have used a recursive function for printing this hierarchy. Let’s understand the flow. Consider the following hierarchy: 
 
hierarchy
 
So, according to this, we will design table like,
 
Folder ID Parent Folder ID Folder Name
1 0 Gujarat
2 0 Maharashtra
3 1 Ahmedabad
4 1 Surat
5 2 Mumbai
6 5 Colaba
7 2 Pune
  • The method print() will first print the root node.
  • In for loop, the folders array is traversed from the current index to the last index to check if the current node’s ID is any of the folder’s Parent ID.
  • If the condition satisfies, the folder name is printed, and the print() method is called again recursively to check and print the folder’s child and so on.
  • visitedIndexes list contains the indexes of already visited and printed nodes so that the loop won’t run for the folder unnecessarily.
INPUT
  1. Enter no.of folders: 7 ** * Folder 1 Details ** * Enter Folder ID: 1  
  2. Enter Parent Folder ID: 0  
  3. Enter Folder Name: Gujarat ** * Folder 2 Details ** * Enter Folder ID: 2  
  4. Enter Parent Folder ID: 0  
  5. Enter Folder Name: Maharashtra ** * Folder 3 Details ** * Enter Folder ID: 3  
  6. Enter Parent Folder ID: 1  
  7. Enter Folder Name: Ahmedabad ** * Folder 4 Details ** * Enter Folder ID: 4  
  8. Enter Parent Folder ID: 1  
  9. Enter Folder Name: Surat ** * Folder 5 Details ** * Enter Folder ID: 5  
  10. Enter Parent Folder ID: 2  
  11. Enter Folder Name: Mumbai ** * Folder 6 Details ** * Enter Folder ID: 6  
  12. Enter Parent Folder ID: 5  
  13. Enter Folder Name: Colaba ** * Folder 7 Details ** * Enter Folder ID: 7  
  14. Enter Parent Folder ID: 2  
  15. Enter Folder Name: Pune  
OUTPUT
 
OUTPUT