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Trail: Learning the Java Language
Lesson: Object Basics and Simple Data Objects

## Answers to Questions and Exercises: Strings

### Questions

> Question 1: What is the initial capacity of the following string buffer?

> >     StringBuffer sb = new StringBuffer("Able was I ere I saw Elba.");

> Answer 1: It's the length of the initial string + 16: 26 + 16 = 42.

> Question 2: Consider the following string:

> >     String hannah = "Did Hannah see bees? Hannah did.";

> > Question 2a: What is the value displayed by the expression `hannah.length()`?
> > Answer 2a: 32.

> > Question 2b: What is the value returned by the method call `hannah.charAt(12)`?
> > Answer 2b: `e`.

> > Question 2c: Write an expression that refers to the letter `b` in the string referred to by `hannah`.
> > Answer 2c: `hannah.charAt(15)`.

> Question 3: How long is the string returned by the following expression? What is the string?

> >     "Was it a car or a cat I saw?".substring(9, 12)

> Answer 3: It's 3 characters in length: `car`. It does not include the space after car.

> Question 4: In the following program, called `ComputeResult`, what is the value of `result` after each numbered line executes?

> >     public class ComputeResult {
> >         public static void main(String[] args) {
> >             String original = "software";
> >             StringBuffer result = new StringBuffer("hi");
> >             int index = original.indexOf('a');

> >     /*1*/   result.setCharAt(0, original.charAt(0));
> >     /*2*/   result.setCharAt(1, original.charAt(original.length()-1));
> >     /*3*/   result.insert(1, original.charAt(4));
> >     /*4*/   result.append(original.substring(1,4));
> >     /*5*/   result.insert(3, (original.substring(index, index+2) + " "));

> >             System.out.println(result);
> >         }
> >     }

> Answer 4:
> 1. si
> 2. se
> 3. swe
> 4. sweoft
> 5. swear oft

### Exercises

> Exercise 1: Show two ways to concatenate the following two strings together to get the string `"Hi, mom."`:

> >     String hi = "Hi, ";
> >     String mom = "mom.";

> Answer 1: `hi.concat(mom)` and `hi + mom`.

> Exercise 2: Write a program that computes your initials from your full name and displays them.
> Answer 2: `ComputeInitials`

> >     public class ComputeInitials {
> >         public static void main(String[] args) {
> >             String myName = "Fred F. Flintstone";
> >             StringBuffer myInitials = new StringBuffer();
> >             int length = myName.length();

> >             for (int i = 0; i < length; i++) {
> >                 if (Character.isUpperCase(myName.charAt(i))) {
> >                     myInitials.append(myName.charAt(i));
> >                 }
> >             }
> >             System.out.println("My initials are: " + myInitials);
> >         }
> >     }

> Exercise 3: An anagram is a word or a phrase made by transposing the letters of another word or phrase; for example, "parliament" is an anagram of "partial men," and "software" is an anagram of "swear oft." Write a program that figures out whether one string is an anagram of another string. The program should ignore white space and punctuation.
> Answer 3: `Anagram`

> >     /**
> >      * This class compiles with v 1.2 and 1.3, but not previous
> >      * versions, because its sort method uses the Arrays class,
> >      * which was added in 1.2.  To make Anagram work with early
> >      * versions of the Java platform, you need to reimplement
> >      * the sort method.
> >      */

> >     public class Anagram {

> >         /**
> >          * Tests whether the passed-in strings are anagrams --
> >          * containing the exact same number of each letter.
> >          * Punctuation, case, and (obviously) order don't matter.
> >          *
> >          * @return true if the strings are anagrams; otherwise, false
> >          */
> >         public static boolean areAnagrams(String string1,
> >                                           String string2) {

> >             String workingCopy1 = removeJunk(string1);
> >             String workingCopy2 = removeJunk(string2);

> >     	workingCopy1 = workingCopy1.toLowerCase();
> >     	workingCopy2 = workingCopy2.toLowerCase();

> >     	workingCopy1 = sort(workingCopy1);
> >     	workingCopy2 = sort(workingCopy2);

> >             return workingCopy1.equals(workingCopy2);
> >         }

> >         /**
> >          * Removes punctuation, spaces -- everything except letters
> >          * and digits from the passed-in string.
> >          *
> >          * @return a stripped copy of the passed-in string
> >          */
> >         protected static String removeJunk(String string) {
> >             int i, len = string.length();
> >       	StringBuffer dest = new StringBuffer(len);
> >     	char c;

> >     	for (i = (len - 1); i >= 0; i--) {
> >     	    c = string.charAt(i);
> >     	    if (Character.isLetterOrDigit(c)) {
> >     		dest.append(c);
> >     	    }
> >     	}

> >             return dest.toString();
> >         }

> >         /**
> >          * Sorts the passed-in string.  Reimplement this method
> >          * if you want to use this class in pre-Java-2 versions
> >          * of the platform.
> >          *
> >          * @return a sorted copy of the passed-in string
> >          */
> >         protected static String sort(String string) {
> >     	int length = string.length();
> >             char[] charArray = new char[length];

> >     	string.getChars(0, length, charArray, 0);

> >     	//NOTE: The following line of code causes pre-1.2
> >     	//compilers to choke.
> >     	java.util.Arrays.sort(charArray);

> >             return new String(charArray);
> >         }

> >         public static void main(String[] args) {
> >             String string1 = "Cosmo and Laine:";
> >             String string2 = "Maid, clean soon!";

> >             System.out.println();
> >             System.out.println("Testing whether the following "
> >                              + "strings are anagrams:");
> >             System.out.println("    String 1: " + string1);
> >             System.out.println("    String 2: " + string2);
> >             System.out.println();

> >             if (areAnagrams(string1, string2)) {
> >                 System.out.println("They ARE anagrams!");
> >             } else {
> >                 System.out.println("They are NOT anagrams!");
> >             }
> >             System.out.println();
> >         }
> >     }

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