ITEC 120 2007spring ibarland, jpittges

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lab14a
iteration
while vs for

1. Write a function countVowels, which takes a String, and returns how many vowels it has. Use a while-loop.
   1. Here are some test cases you can paste into the (khaki green) unit-test class:

      assertEquals( 0, Linguistics.countVowels( "" ) ); assertEquals( 0, Linguistics.countVowels( "z" ) ); assertEquals( 0, Linguistics.countVowels( "zxyz" ) ); assertEquals( 1, Linguistics.countVowels( "a" ) ); assertEquals( 1, Linguistics.countVowels( "A" ) ); assertEquals( 0, Linguistics.countVowels( "y" ) ); assertEquals( 0, Linguistics.countVowels( "Y" ) ); assertEquals( 5, Linguistics.countVowels( "aeiou" ) ); assertEquals( 5, Linguistics.countVowels( "AEIOU" ) ); assertEquals( 1, Linguistics.countVowels( "Zyzzyva" ) ); assertEquals( 4, Linguistics.countVowels( "Test Cases, Eh?" ) ); assertEquals( 5, Linguistics.countVowels( "abcdefghijklmnopqrstuvwxyz" ); assertEquals( 0, Linguistics.countVowels( "$%^#!" ) );

      Note that this is not an unusually large set of test cases, in real-world terms.
   2. For good style, first define a named-constant VOWELS to be the "AaEeIiOoUu".

   3. One of the questions we ask ourselves, when writing a loop, is “how do I do a small task once”? In this case, that's “how do I tell if one particular character is a vowel”?

      You should be able to answer this question after perusing standard Java documentation for Strings. Here is what you'd end up with: an expression that tells whether the 17th character of a String s is a vowel:

      VOWELS.contains( new Character( s.charAt(16) ).toString() )

      Note that we have to convert a single character into a String (which is a sequence of 0-or-more-characters). We do this by using the wrapper class Character, and its toString method.

   4. Often when writing code, you refer to similar functions, just to get the syntax correct. See below for a while-loop (from lecture) which addes all the ages Dogs in a certain list.
   5. Optional, but easy: It's a pain that our named constant has to include both upper- and lower-case versions. Modify your code so that if you decide to count 'y' as a vowel, you only have to add one character to VOWELS, not two
   6. Optional, if you have finished the entire lab:
      Make a second method which tells how many characters of a String occur in some other “reference” String. For example, how many letters occur in the word "creations" (which happens to have all the most common letters in English).
      Make sure that when you're done, your vowel-counting function is just a single line.
2. Modify your method so that it uses a for loop (not a for-each loop). Yikes, we haven't talked about these old-school for loops! They turn out to be handy when you want a loop-variable (an index) which just counts from one number to another (e.g. 0 to n, or a to b).
   • Review a while-loop (from lecture) which adds up the total age of all Dogs in a list:

     // Assume 'doggies' is a variable of type a LinkList<Dog>. int totalAgeSoFar = 0; int index = 0; while (index < doggies.size()) { totalAgeSoFar = totalAgeSoFar + (doggies.get(index)).getAge(); index=index+1; }

   • Here's the exact same task, written using this new “for” loop:

     int totalAgeSoFar = 0; for ( int index = 0; index < doggies.size(); index=index+1 ) { totalAgeSoFar = totalAgeSoFar + (doggies.get(index)).getAge(); }

     Note that both loops have
     • loop-variable initialization
     • a loop-condition
     • an end-of-loop update to the loop-variable.
     These three parts are all dealing with the loop's control-logic. In the for loop, all three occur together on the same line. Notice that they are separated by semicolons (“;”).
   • By following the pattern of how the while and for relate to each other, take your vowel-counting program and write a for-loop version. (We know that you haven't seen the old-school-for-loop before, but the skill of taking the examples and following its punctuation carefully is a useful skill.)
   Details of the official syntax for the for-loop is on the lecture notes; we'll review it Thurs.
3. Optional: write a method which takes in a string, and determines whether it's a palindrome -- whether it reads the same forwards and backwards. For instance, if you are ignoring case, "ava" and "MadamImAdam" are both palindromes¹.

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