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:

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

Enter no.of folders: 7 ** * Folder 1 Details ** * Enter Folder ID: 1
Enter Parent Folder ID: 0
Enter Folder Name: Gujarat ** * Folder 2 Details ** * Enter Folder ID: 2
Enter Parent Folder ID: 0
Enter Folder Name: Maharashtra ** * Folder 3 Details ** * Enter Folder ID: 3
Enter Parent Folder ID: 1
Enter Folder Name: Ahmedabad ** * Folder 4 Details ** * Enter Folder ID: 4
Enter Parent Folder ID: 1
Enter Folder Name: Surat ** * Folder 5 Details ** * Enter Folder ID: 5
Enter Parent Folder ID: 2
Enter Folder Name: Mumbai ** * Folder 6 Details ** * Enter Folder ID: 6
Enter Parent Folder ID: 5
Enter Folder Name: Colaba ** * Folder 7 Details ** * Enter Folder ID: 7
Enter Parent Folder ID: 2
Enter Folder Name: Pune

OUTPUT