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Lesson: Numbers and Strings
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Answers to Questions and Exercises: Characters and Strings


  1. Question: What is the initial capacity of the following string builder?

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

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

  2. Consider the following string:

    String hannah = "Did Hannah see bees? Hannah did.";
    1. Question: What is the value displayed by the expression hannah.length()?

      Answer: 32.

    2. Question: What is the value returned by the method call hannah.charAt(12)?

      Answer: e.

    3. Question: Write an expression that refers to the letter b in the string referred to by hannah.

      Answer: hannah.charAt(15).

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

  4. Question: 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";
            StringBuilder result = new StringBuilder("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) + " ")); 


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


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

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

    Answer: hi.concat(mom) and hi + mom.

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

    Answer: 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))) {
            System.out.println("My initials are: " + myInitials);
  3. Exercise: 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: Anagram

    public class Anagram {
        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);
        protected static String removeJunk(String string) {
            int i, len = string.length();
            StringBuilder dest = new StringBuilder(len);
      		char c;
    	    for (i = (len - 1); i >= 0; i--) {
    	        c = string.charAt(i);
    	        if (Character.isLetter(c)) {
            return dest.toString();
        protected static String sort(String string) {
    	    char[] charArray = string.toCharArray();
            return new String(charArray);
        public static void main(String[] args) {
            String string1 = "Cosmo and Laine:";
            String string2 = "Maid, clean soon!";
            System.out.println("Testing whether the following "
                             + "strings are anagrams:");
            System.out.println("    String 1: " + string1);
            System.out.println("    String 2: " + string2);
            if (areAnagrams(string1, string2)) {
                System.out.println("They ARE anagrams!");
            } else {
                System.out.println("They are NOT anagrams!");

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