List Files in a directory

I remembered a good question which I was asked in one of my interviews some time back...

Write a program to list the files in a directory. The listed files should be greater than 1000 KB and it should be sorted.

This should take care of recursion also. Also write test cases for the same.

Here is what I came up with...

Java Program to List Files in a Directory.

/*
This program prints all the files in a directory(including sub directories recursively)
- more than 1000 KB - 1 KB = 1000 Bytes, 1000 KB = 1024000 bytes
- in descending order
*/

import java.io.*;
import java.util.*;

public class listFiles{
// Vector to hold all the list of files.
static Vector v1 = new Vector();
static boolean validdir = true;

public static void main(String[] args) {
// Get the directory name from the command line
if (args.length > 0 ) {
File dirName = new File(args[0].trim());
listFiles.listFilesinDir(dirName);
} else {
System.out.println("Enter a directory name.\n Usage: listFiles dirName");
validdir = false;
}

if (validdir) {
// Sort the Vector v1
Comparator comparator = Collections.reverseOrder();
// System.out.println("The List of files before sorting: " + v1);

Collections.sort(v1,comparator);
//System.out.println("The List of files after sorting in descending order : " + v1);
System.out.println("The Total Number of Files are: " + v1.size());

for (Enumeration e = v1.elements(); e.hasMoreElements();) {
System.out.println(e.nextElement());
}
}
} // end main()

public static void listFilesinDir(File fin) {
// Throw error if the directory does not exist.
if (!fin.exists()) {
validdir = false;
System.out.println(fin.getName() + " does not exist!!!");
return;
}

if (fin.isFile()) {
// 1 KB = 1000 Bytes, 1000 KB = 1024000 bytes
if (fin.length() > 1024000) {
// To print all files remove the comment in the below line.
// System.out.println(fin.getName());
// Add all the files into the vector.
listFiles.v1.add(fin.getName());
}
}
else if (fin.isDirectory()) {
String[] files = fin.list();
if (files == null) return;

for (int i=0; i

Here is the list of TestCases

	A	B	C	D	E
1	Nu	Test Case For	Description	Expected Results	Remarks
2	1	Valid Dir Name	Give a Valid Dir Name	Should give the list of files	Assume that size and ascending is taken care
3	2	Valid Dir Name - Order	Check for Descending order	The listed files should be in descending order	Assume that size is taken care
4	3	Valid Dir Name - Size	Check for the Size of Files	The listed files should be greater than 1000 KB only	Assume that ascending is taken care
5	4	Size - Boundary values	Have a file of Exactly 1000 KB	This file should be listed	Assume that ascending is taken care
6	5	Size - Boundary values	Have a file of Exactly 1001 KB	This file should be listed	Assume that ascending is taken care
7	6	Size - Boundary values	Have a file of Exactly 999 KB	This file should NOT be listed
8	7	Size - Low size	Have a empty file/0 size	This file should NOT be listed
9	8	Size - Low size	Have a file of 1 KB size	This file should NOT be listed
10	9	Size - Huge Size	Have a file of 20000 KB	This file should be listed	Assume that ascending is taken care
11	10	Order	Have files with names - a.txt, aa.txt, aaa.txt	Observe that these should be sorted in descending order	Assume that size is taken care
12	11	Order	Have files with names - a.txt, b.txt, c.txt	Observe that these should be sorted in descending order	Assume that size is taken care
13	12	Dir Name -Space	Let the directory name have space - ex: "Program Files"	Should give the list of files	Assume that size and ascending is taken care
14	13	Dir Name - Case Sensitive	Have directories with case sensitive - ex: myDir1, mYdIR2 etc	Should give the list of files	Assume that size and ascending is taken care
15	14	Sub Directories	Have many sub directories	The sub directory names should NOT be listed
16	15	Sub Directories	Have many sub directories	The files inside the sub directories should be listed	Assume that size and ascending is taken care
17	16	Sub Directories	Have a sub directory with the "same name" as parent	The files inside the sub directories should be listed	Assume that size and ascending is taken care
18	17	Hidden Files	Have some hidden files in the dir	These should be listed	Assume that size and ascending is taken care
19	18	Hidden Directory	Specify a hidden dir as input	The files inside a hidden dir should be listed	Assume that size and ascending is taken care
20	19	Hidden sub directories	Have some hidden sub directories inside the parent dir	The files inside a hidden dir should be listed	Assume that size and ascending is taken care
21	20	Read-Only Files	Have some read only files in the dir	These should be listed
22	21	Read-only Directory	Specify a read-only dir as input	The files inside a read-only dir should be listed	Assume that size and ascending is taken care
23	22	Read-only Sub directories	Have some read-only sub directories inside the parent dir	The files inside a read-only dir should be listed	Assume that size and ascending is taken care
24	23	Empty Dir	Give a valid dir name - but empty one	No Files should be listed
25	24	Dir Name - Special Chars	Have some special chars in the name of the dir	Should give the list of files	Assume that size and ascending is taken care
26	25	Sub Directories - Breadth	Have many sub directories in the parent dir… Have a breadth of say 10-20 dirs. and files inside those directories	Should give the list of files	Assume that size and ascending is taken care
27	26	Sub Directories - Depth	Have a sub directoy inside a sub directory inside a sub dir…. Have a depth of say 10-20 dirs. and files inside those directories	Should give the list of files	Assume that size and ascending is taken care
28	27	Shared Dir in Windows	Specify a shared directory	Should give the list of files	Assume that size and ascending is taken care
29	28	Specify the URI as dir name	A dir on the intranet - ex: \\10.192.23.212\myDir1	Should give the list of files if accessible	Assume that size and ascending is taken care
30	29	Dir Name - "."	Specify "." as the dir name	Should give the list of files in the current dir	Assume that size and ascending is taken care
31	30	Dir Name - ".."	Specify ".." as the dir name	Should give the list of files in the parent dir	Assume that size and ascending is taken care
32	31	Dir Name - Absolute Path - Forward Slash	Specify "C:/Testing/MyDir1" as the dir name	Should give the list of files	Assume that size and ascending is taken care
33	32	Dir Name - Absolute Path - Back Slash	Specify "C:\Testing\MyDir1" as the dir name	Should give the list of files	Assume that size and ascending is taken care
34	33	Dir Name - Relative Path - Forward slash	Specify "MyDir1/MyDir2/MyDir3" as the dir name	Should give the list of files	Assume that size and ascending is taken care
35	34	Dir Name - Relative Path - Backward slash	Specify "MyDir1\MyDir2\MyDir3" as the dir name	Should give the list of files	Assume that size and ascending is taken care
36	35	Dir Name - Relative Path	Specify "..\..\MyDir2\MyDir3" as the dir name	Should give the list of files	Assume that size and ascending is taken care
37	36	Dir Name - integer	The dir name is "12345"	Should give the list of files	Assume that size and ascending is taken care
38	37	Dir Name - very long name	Ex: The dir name is "Thisismydirectoryandthenameisverybig"	Should give the list of files	Assume that size and ascending is taken care
39	38	Negative Test	Specify some file name as input	Throw error message
40	39	Negative Test	Specify some non existing dir name	Throw error message
41	40	Negative Test	Specify null	Throw error message
42	41	Formats	All possible format files should be listed - ex: ".zip" ".doc" ".pdf" etc	Should give the list of files	Assume that size and ascending is taken care
43	42	Negative Test	Specify a zip file as input	Throw error message
44	43	Negative Test	Specify the dir name + some blanks	Should trim
45
46		Unix/Linux
47	44	Perform all the above tests for Linux/Unix; Also perform the below special cases for Unix
48
49	45	Dir Name - Mounted dir	Specify a mounted dir as the input dir name	Should give the list of files	Assume that size and ascending is taken care
50	46	Dir Name - Case Sensitive	Have directories with case sensitive - ex: myDir1, mYdIR2 etc	Should give the list of files	Assume that size and ascending is taken care
51	47	Read-Only Files	Have some read only files in the dir	These should be listed
52	48	Read-only Directory	Specify a read-only dir as input	The files inside a read-only dir should be listed	Assume that size and ascending is taken care
53	49	Read-only Sub directories	Have some read-only sub directories inside the parent dir	The files inside a read-only dir should be listed	Assume that size and ascending is taken care
54	50	Dir Name - Special Chars	Have some special chars in the name of the dir	Should give the list of files	Assume that size and ascending is taken care
55	51	Dir Name - "."	Specify "." as the dir name	Should give the list of files in the current dir	Assume that size and ascending is taken care
56	52	Dir Name - ".."	Specify ".." as the dir name	Should give the list of files in the parent dir	Assume that size and ascending is taken care
57	53	Dir Name - Absolute Path - Forward Slash	Specify "/opt/testing/MyDir1" as the dir name	Should give the list of files	Assume that size and ascending is taken care
58	54	Dir Name - Absolute Path - Back Slash	Specify "opt\testing\MyDir1" as the dir name	Should give the list of files	Assume that size and ascending is taken care
59	55	Dir Name - Relative Path - Forward slash	Specify "MyDir1/MyDir2/MyDir3" as the dir name	Should give the list of files	Assume that size and ascending is taken care
60	56	Dir Name - Relative Path - Backward slash	Specify "MyDir1\MyDir2\MyDir3" as the dir name	Should give the list of files	Assume that size and ascending is taken care
61	57	Dir Name - Relative Path	Specify "..\..\MyDir2\MyDir3" as the dir name	Should give the list of files	Assume that size and ascending is taken care
62
63		Performance Testing
64	58	50,000 Files( all > 1000 KB)	Have a dir with 50,000 Files	Should give the list of files - check for breakdown	Assume that size and ascending is taken care
65	59	50,000 Files > 1000 KB + 50,000 Files < 1000 KB	Have a dir with 50,000 Files > 1000 KB and 50,000 Files < 1000 KB	Should give the list of files - check for breakdown	Assume that size and ascending is taken care
66
67	60	10,000 Sub directories	Have 10,000 sub directories with files	Should give the list of files - check for breakdown	Assume that size and ascending is taken care