Chapter 30

Write an application that reads a line of text, tokenizes it using space characters as delimiters and outputs only those words ending with the letters "ED".

Write an application that inputs an integer code for a character and displays the corresponding character. Modify this application so that it generates all possible three-digit codes in the range from 000 to 255 and attempts to print the corresponding characters.

Write your own versions of String search methods indexof and lastIndexof.

Write an application that reads a five-letter word from the user and produces every possible three-letter string that can be derived from the letters of that word. For example, the three-letter words produced from the word "bathe" include "ate," "bat," "bet," "tab," "hat," "the" and "tea."

(Text Analysis) The availability of computers with string-manipulation capabilities has resulted in some rather interesting approaches to analyzing the writings of great authors. Much attention has been focused on whether William Shakespeare ever lived. Some scholars believe there is substantial evidence indicating that Christopher Marlowe actually penned the masterpieces attributed to Shakespeare. Researchers have used computers to find similarities in the writings of these two authors. This exercise examines three methods for analyzing texts with a computer. a) Write an application that reads a line of text from the keyboard and prints a table indicating the number of occurrences of each letter of the alphabet in the text. For example, the phrase To be, or not to be: that is the question: contains one “a,” two “b’s,” no “c’s,” and so on. b) Write an application that reads a line of text and prints a table indicating the number of one-letter words, two-letter words, three-letter words, and so on, appearing in the text. For example, Fig. 30.25 shows the counts for the phrase Whether 'tis nobler in the mind to suffer c) Write an application that reads a line of text and prints a table indicating the number of occurrences of each different word in the text. The first version of your application should include the words in the table in the same order in which they appear in the text. For example, the lines To be, or not to be: that is the question: Whether 'tis nobler in the mind to suffer contain the word “to” three times, the word “be” two times, the word “or” once, and so on. A more interesting (and useful) printout should then be attempted in which the words are sorted alphabetically.

(Printing Dates in Various Formats) Dates are printed in several common formats. Two of the more common formats are 04/25/1955 and April 25, 1955 Write an application that reads a date in the first format and prints it in the second format.

(Check Protection) Computers are frequently employed in check-writing systems, such as payroll and accounts payable applications. There are many strange stories about weekly paychecks being printed (by mistake) for amounts in excess of \(\$ 1\) million. Incorrect amounts are printed by computerized check- writing systems because of human error or machine failure. Systems designers build controls into their systems to prevent such erroneous checks from being issued. Another serious problem is the intentional alteration of a check amount by someone who plans to cash a check fraudulently. To prevent a dollar amount from being altered, some computerized check-writing systems employ a technique called check protection. Checks designed for imprinting by computer contain a fixed number of spaces in which the computer may print an amount. Suppose a paycheck contains eight blank spaces in which the computer is supposed to print the amount of a weekly paycheck. If the amount is large, then all eight of the spaces will be filled. For example, 1,230.60 (check amount) 12345678 (position numbers) On the other hand, if the amount is less than \(\$ 1000\), then several of the spaces would ordinarily be left blank. For example, 99.87 \-------- 12345678 contains three blank spaces. If a check is printed with blank spaces, it is easier for someone to alter the amount of the check. To prevent a check from being altered, many check-writing systems insert leading asterisks to protect the amount as follows: ***99.87 \-------- 12345678 Write an application that inputs a dollar amount to be printed on a check, then prints the amount in check-protected format with leading asterisks if necessary. Assume that nine spaces are available for printing the amount.

Write an application that will assist the user with metric conversions. Your application should allow the user to specify the names of the units as strings (i.e., centimeters, liters, grams, and so on, for the metric system and inches, quarts, pounds, and so on, for the English system and should respond to simple questions, such as "How many inches are in 2 meters?" "How many liters are in 10 quarts?" Your application should recognize invalid conversions. For example, the question "How many feet are in 5 kilograms?" is not meaningful because "feet" is a unit of length, whereas "kilograms" is a unit of mass.

Many popular word-processing software packages have built-in spell checkers. In this project, you are asked to develop your own spell-checker utility. We make suggestions to help get you started. You should then consider adding more capabilities. Use a computerized dictionary (if you have access to one) as a source of words. Why do we type so many words with incorrect spellings? In some cases, it is because we simply do not know the correct spelling, so we make a best guess. In some cases, it is because we transpose two letters (e.g., "defualt" instead of "default"). Sometimes we double-type a letter accidentally (e.g., "hanndy" instead of "handy"). Sometimes we type a nearby key instead of the one we intended (e.g., "biryhday" instead of "birthday"), and so on. Design and implement a spell-checker application in Java. Your application should maintain an array wordList of strings. Enable the user to enter these strings. [Note: In Chapter \(14,\) we have introduced file processing. With this capability, you can obtain the words for the spell checker from a computerized dictionary stored in a file.] Your application should ask a user to enter a word. The application should then look up that word in the wordList array. If the word is in the array, your application should print "Word is spelled correctly." If the word is not in the array, your application should print "Word is not spelled correctly." Then your application should try to locate other words in wordList that might be the word the user intended to type. For example, you can try all possible single transpositions of adjacent letters to discover that the word "default" is a direct match to a word in wordList. Of course, this implies that your application will check all other single transpositions, such as "edfault," "dfeault," "deafult," "defalut" and "defautl." When you find a new word that matches one in wordList, print it in a message, such as Did you mean "default"? Implement other tests, such as replacing each double letter with a single letter, and any other tests you can develop to improve the value of your spell checker.