created 05/08/00


Programming Exercises


Exercise 1 ― Junk Mail Generator

Write a program that creates a "personalized" letter, given a form letter and a person's name. The form letter is an input file of text (use file redirection as discussed in chapter 23). The person's name is a command line argument. The file is normal text, but with a * wherever a person's name should be substituted. For example:

Dear *,

I have exciting news for you, *!!! For just $49.99 plus postage
and handling you, *, can be the proud owner of a genuine leather
mouse pad!  No more finger strain for you, *, as you surf the web
with style.

Act Soon,

Venture Marketing Corp.

Assume the above is in a file junk.txt. A run of the program outputs:

C:\chap49D>java  JunkGenerator "Occupant" < junk.txt
Dear Occupant,

I have exciting news for you, Occupant!!! For just $49.99 plus postage
and handling you, Occupant, can be the proud owner of a genuine leather
mouse pad!  No more finger strain for you, Occupant, as you surf the web
with style.

Act Soon,

Venture Marketing Corp.

C:\chap49D>

Write the program so that it will substitute for any number of * on one line, and accepts any number of lines as input. The main program loop will be a while loop that continues until the input string (read with readLine() is null. Each input line should be used to create a StringTokenizer with appropriate delimiters.

If you wish to avoid the command line argument, ask the user for the occupant name and input it in the usual way.

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Exercise 2 ― Word Reverser

Write a program that reads in a sentence from the user and prints it out with each word reversed, but with the words and punctuation in the original order:

C:\> java reverseSent 
Input:  Go to the main menu.
oG ot eht niam unem.

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Exercise 3 ― ISBN Verifier

An International Standard Book Number (ISBN) is a code that uniquely identifies an edition of a book. The ISBN consists of ten digits separated by dashes into groups. The groups are of various sizes, except for the last group. The last group is always a single character, '0' through '9' or 'X', and acts as a check on the rest of the digits.

0-670-03441-X
0-201-48558-3
1-56592-262-X
0-06-027900-1
0-439-45695-9
0-470-84371-3
1-4000-3136-2
0-19-856453-8
1-85671-104-8

The last character is calculated from the other 9 digits:

  1. Multiply the first digit by 10.
  2. Multiply the second digit by 9.
  3. Multiply the second digit by 8.
  4. . . .
  5. Multiply the ninth digit by 2.
  6. Add up all these values.
  7. Divide the sum by 11.
  8. Take the remainder.
  9. Subtract the remainder from 11. This is the check digit.
  10. If the remainder is 10, use an 'X'

For example:

0-201-48558-3

0 * 10 =  0
2 *  9 = 18
0 *  8 =  0
1 *  7 =  7
4 *  6 = 24
8 *  5 = 40
5 *  4 = 20
5 *  3 = 15
8 *  2 = 16
        -----
sum =   140

140 / 11 = 12 rem 8

11 - 8 = 3 <-- the check digit

Write a program that prompts the user for an ISBN and then checks if the ISBN is correct. Calculate a check character from the first nine digits and compare it to the last character of the ISBN. If the two do not agree, the ISBN is incorrect.


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End of Exercises.