Lab 11, Esc101, 2004-05 Semester-II

Solve the following problems

Problem 1

Write a program that asks the user for a file name and that prints the number of lines in that file. The program wc can be used  to count the number of lines in a file.  For instance, wc -l Test.java, will give the number of lines in the file Test.java


Problem 2   

Write a program Find that searches all files specified on the command line and prints out all lines containing a keyword. For example, if you call

java Find Buff report.txt address.txt Homework.java

then the program might print

report.txt:  Buffer style lunch will be available at the
address.txt:  Buffet, Warren|11801 Trenton Court| Dallas|TX
address.txt:  Walters, Winnie| 59 Timothy Circle| Buffalo|MI
Homework.java: BufferedReader in;

The keyword is always the first command line argument.
Extra Credit

Problem 3    Playfair cipher

In this you have to encrypt and decrypt a file. Encryption is done with pairs of letters together. You pick a keyword and remove duplicate letters from it. Then you fill the keyword, and the remaining letters of the alphabet, into a  5 X 5  square. (Since there are only 25 squares, I and J are considered the same letter.)  Here is such an arrangement with the keyword PLAYFAIR:

P  L  A  Y  F
I   R  B  C  D
E  G  H  K  M
N  O  Q  S  T
U  V  W  X  Z

To encrypt a letter pair, say AT, look at the rectangle with corners A and T:  The encoding of this pair is formed by looking at the other two corners of the rectangle-- in this case, FQ. If both letters happen to be in the same row or column, such as GO, simply swap the two letters. Decryption is done in the same way.
    Write a program which encrypts a given file and writes to a second file.  For example, java Encrypt test.txt playfair enc.txt should encrypt the contents of the file test.txt and write onto file enc.txt using the keyword "playfair".  Also write a similar program Decrypt to decrypt a given file and write onto another file.