Assignment 4
Objective
This assignment should give you practice with accessing the file system using the Java File class
as well as the basics of using input/output streams.
Task
Write a file viewer that allows you to view file information, view directory structure, read text
files, and copy files. Your main program should be run from the file:
FileViewer.java
You should not need any other files or classes, but you may create them if you wish
Each file should have a comment including your name at the top of the file. Each file
should also have appropriate comments throughout.
Requirements
1. Command Line Options: Your program should accept the following command line options:
“-i” (for (i)nformation) with an optional file or directory as a 2nd parameter. If no 2nd
parameter is passed, default to the current directory “.”
“-v” (for (v)iew) with a file to view as the 2nd parameter
“-c” (for (c)opy) with a sourcefile as the 2nd parameter and a destination file as the 3rd
parameter
If no parameters are passed, then the program should default to displaying information
on the current directory (as if the user had passed “-i .”)
If the command is invalid usage (illegal options), print a usage message, as below, then exit
the program:
Usage: java .jar hw4. jar [. i[< file >|<directory >]|.v <file >|.c <sourceFile ><destFile >]
Since that text has to be small to fit on the line, I’ll break it up into multiple lines here (make
sure you print it all on one line in your code):
Usage: java -jar hw4.jar
[-i [<file>|<directory>]|-v <file>|-c <sourceFile> <destFile>]
Information: When the user requests information using the “-i” option, they may pass a 2nd
parameter indicating the file or directory they wish information on. This is handled in
different ways, depending on whether it is a file or directory. If it is a file:
Print the absolute path to the file
Indicate whether the file can be executed
Print out the file size in bytes
2
Print out the last modified date of the file
Your output should match mine exactly (see the example output for the exact format)
However, if it is a directory:
Print a heading indicating that you are printing size followed by filename
Give each file on which you are printing the size, followed by the filename
Sort the files by filesize (lowest to highest)
See example output for details
If the 2nd parameter is not a regular file or directory, print the error message:
“Error: Invalid File”
2. View: If the user requests to view a file, the 2nd parameter should be a regular file. If the
file is not found, print an appropriate error message. You should then print the contents of
the file, as text, to the screen. Remember to handle all exceptions you encounter.
3. Copy: If the user requests to copy a file, the 2nd parameter should be the name of a regular
file (the source file) and the 3rd parameter should be the name of the file to copy to (the
destination file). If the destination file already exists, print an appropriate error message. If
the source file is not valid, print an appropriate error message. Then you should copy the
information from the source file to the destination file, handling any exceptions
encountered appropriately. After this, print a message to the user stating that the copy was
successful. Please note that you should be able to copy binary files with this method, not
just text files.
4. Other Requirements:
Make sure you handle all exceptions that could be thrown when dealing with the file I/O.
When printing error messages to the user, you do not have to match my format exactly
(although it is preferred).
For all other output, match my format and text exactly
5. Extra Credit: You may earn extra credit on this assignment by allowing the user to specify an
additional command-line option: “-d” for compare (d)ifferences in files. This option should
take 2 more parameters, both of which should be files. It should compare the two files and
print a message indicating whether they are the same. As in the other options, handle
exceptions. Please note that this changes the usage message. The new usage message is as
follows (Please note this is on multiple lines, but your actual message should all print on the
same line)
Usage: java -jar hw4.jar [-i [<file>|<directory>]|
-v <file>|-c <sourceFile> <destFile>|-d <file1> <file2>]
6. Hints:
Remember that file sizes are returned via the length() function and are of type
long (which can be converted to type Long using a class method of class Long)
You can print the last modified date using the Java Date class along with a
SimpleDateFormat class. Here is a good place to start:
https://docs.oracle.com/javase/tutorial/i18n/format/simpleDateFormat.html
3
You could also print the last modified date using printf. Look at the Formatter class
for a detailed listing of the date/time flags. Remember to use the “<” flag as well to keep
using the same parameter (so you don’t have to pass the date in multiple times). As an
example:
System.out.printf(“%b %<d %<Y”, date)
would print out
Jan 31 2021
if the variable date was a long integer representing the date Jan 31, 2021.
The display option only has to handle text files, all other options should handle binary
files as well.
You may use System.exit(0) to exit the program at any time
Some Helpful Classes/Methods
String.equals(Object)
String.charAt(int)
File class
Arrays.sort(T[], Comparator)
Comparator Interface
Date(long)
DateFormat.format(Date)
Long.valueOf(long)
Sample Output
(This example has the extra credit implemented)
(commands are underlined)
(these commands were all issued in order in the same directory)
java -jar hw4.jar
Size Filename
26 manifest.mf
767 FileViewer$2.class
767 FileViewer$1.class
1018 aTextFile
1018 aCopyOfATextFile
5608 FileViewer.java
6063 FileViewer.class
6520 hw4.jar
java -jar hw4.jar -i ˜/cop3252/
4
Size Filename
4096 classExamples*
4096 hw*
4096 exams*
4096 lec*
java -jar hw4.jar -i aTextFile
File Path: /home/faculty/brodhead/cop3252/hw/hw4/aTextFile
Is executable? false
Size: 1018 bytes
Last Modified Date: Wed Oct 21 15:00:23
java -jar hw4.jar -v aTextFile
“Jabberwocky”
’Twas brillig, and the slithy toves
Did gyre and gimble in the wabe;
All mimsy were the borogoves,
And the mome raths outgrabe.
“Beware the Jabberwock, my son!
The jaws that bite, the claws that catch!
Beware the Jubjub bird, and shun
The frumious Bandersnatch!”
He took his vorpal sword in hand:
Long time the manxome foe he sought
So rested he by the Tumtum tree,
And stood awhile in thought.
And as in uffish thought he stood,
The Jabberwock, with eyes of flame,
Came whiffling through the tulgey wood,
And burbled as it came!
One, two! One, two! and through and through
The vorpal blade went snicker-snack!
He left it dead, and with its head
He went galumphing back.
“And hast thou slain the Jabberwock?
Come to my arms, my beamish boy!
O frabjous day! Callooh! Callay!”
He chortled in his joy.
’Twas brillig, and the slithy toves
5
Did gyre and gimble in the wabe;
All mimsy were the borogoves,
And the mome raths outgrabe.
— from Through the Looking-Glass, and What Alice Found There
(1871)
java -jar hw4.jar -c aTextFile aCopyOfATextFile
File aCopyOfATextFile already exists.
rm aCopyOfATextFile
ls
FileViewer$1.class FileViewer$2.class FileViewer.class
FileViewer.java aTextFile hw4.jar manifest.mf
java -jar hw4.jar -c aTextFile aCopyOfATextFile
File aTextFile was copied to file aCopyOfATextFile successfully.
java -jar hw4.jar
Size Filename
26 manifest.mf
767 FileViewer$2.class
767 FileViewer$1.class
1018 aTextFile
1018 aCopyOfATextFile
5608 FileViewer.java
6063 FileViewer.class
6520 hw4.jar
java -jar hw4.jar -d aTextFile aCopyOfATextFile
The two files aTextFile and aCopyOfATextFile are the same.
java -jar hw4.jar -d aTextFile FileViewer.class
The two files aTextFile and FileViewer.class are not the same.
Submitting
Pack all of your files (class files and source code) into a fully runnable JAR file called hw4.jar.
The main program that the jar file should execute should be in class FileViewer. I should be
able to run the main() method from your file with the command:
java -jar hw3.jar
Submit your jar file via the Canvas submission link for Assignment 4.
