Wrap-Up

Answers to Self Review Exercises

29.1	False. String objects that are compared using operator == are compared to determine whether they are the same object in memory. False. String objects are immutable and cannot be modified after they are created. StringBuffer objects can be modified after they are created.
29.2	s1.equals( s2 ) s1 += s2; s1.length()

Exercises

29.3	Write an application that uses String method compareTo to compare two strings input by the user. Output whether the first string is less than, equal to or greater than the second.
29.4	Write an application that uses String method regionMatches to compare two strings input by the user. The application should input the number of characters to be compared and the starting index of the comparison. The application should state whether the strings are equal. Ignore the case of the characters when performing the comparison.
29.5	Write an application that uses random-number generation to create sentences. Use four arrays of strings called article, noun, verb and preposition. Create a sentence by selecting a word at random from each array in the following order: article, noun, verb, preposition, article and noun. As each word is picked, concatenate it to the previous words in the sentence. The words should be separated by spaces. When the final sentence is output, it should start with a capital letter and end with a period. The application should generate 20 sentences and output them to a text area. The article array should contain the articles "the", "a", "one", "some" and "any"; the noun array should contain the nouns "boy", "girl", "dog", "town" and "car"; the verb array should contain the verbs "drove", "jumped", "ran", "walked" and "skipped"; the preposition array should contain the prepositions "to", "from", "over", "under" and "on". After the preceding application is written, modify it to produce a short story consisting of several of these sentences. (How about the possibility of a random term-paper writer?)
29.6	(Limericks) A limerick is a humorous five-line verse in which the first and second lines rhyme with the fifth, and the third line rhymes with the fourth. Using techniques similar to those developed in Exercise 29.5, write a Java application that produces random limericks. Polishing this application to produce good limericks is a challenging problem, but the result will be worth the effort!
29.7	(Pig Latin) Write an application that encodes English-language phrases into pig Latin. Pig Latin is a form of coded language. There are many different ways to form pig Latin phrases. For simplicity, use the following algorithm: To form a pig Latin phrase from an English-language phrase, tokenize the phrase into words with an object of class StringTokenizer. To translate each English word into a pig Latin word, place the first letter of the English word at the end of the word and add the letters "ay." Thus, the word "jump" becomes "umpjay," the word "the" becomes "hetay," and the word "computer" becomes "omputercay." Blanks between words remain as blanks. Assume the following: The English phrase consists of words separated by blanks, there are no punctuation marks and all words have two or more letters. Method printLatinWord should display each word. Each token returned from nextToken is passed to method printLatinWord to print the pig Latin word. Enable the user to input the sentence. Keep a running display of all the converted sentences in a text area.
29.8	Write an application that inputs a telephone number as a string in the form [phone]. The application should use an object of class StringTokenizer to extract the area code as a token, the first three digits of the phone number as a token and the last four digits of the phone number as a token. The seven digits of the phone number should be concatenated into one string. Both the area code and the phone number should be printed. Remember that you will have to change delimiter characters during the tokenization process.
29.9	Write an application that inputs a line of text, tokenizes the line with an object of class StringTokenizer and outputs the tokens in reverse order. Use space characters as delimiters.
29.10	Use the string-comparison methods discussed in this chapter and the techniques for sorting arrays developed in Chapter 16 to write an application that alphabetizes a list of strings. Allow the user to enter the strings in a text field. Display the results in a text area.
29.11	Write an application that inputs a line of text and outputs the text twiceonce in all uppercase letters and once in all lowercase letters.
29.12	Write an application that inputs a line of text and a search character and uses String method indexOf to determine the number of occurrences of the character in the text.
29.13	Write an application based on the application in Exercise 29.12 that inputs a line of text and uses String method indexOf to determine the total number of occurrences of each letter of the alphabet in the text. Uppercase and lowercase letters should be counted together. Store the totals for each letter in an array, and print the values in tabular format after the totals have been determined.
29.14	Write an application that reads a line of text, tokenizes the line using space characters as delimiters and outputs only those words beginning with the letter "b".
29.15	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".
29.16	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.
29.17	Write your own versions of String search methods indexOf and lastIndexOf.
29.18	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 the five-letter word. For example, the three-letter words produced from the word "bathe" include "ate," "bat," "bet," "tab," "hat," "the" and "tea."