Answers to Questions and Exercises: Characters and Strings
Questions
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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.
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Consider the following string:
String hannah = "Did Hannah see bees? Hannah did.";
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Question: What is the value displayed by the expression
hannah.length()
?Answer: 32.
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Question: What is the value returned by the method call
hannah.charAt(12)
?Answer:
e
. -
Question: Write an expression that refers to the letter
b
in the string referred to byhannah
.Answer:
hannah.charAt(15)
.
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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. -
Question: In the following program, called
ComputeResult
, what is the value ofresult
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) + " ")); System.out.println(result); } }
Answer:
- si
- se
- swe
- sweoft
- swear oft
Exercises
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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)
andhi + mom
. -
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))) { myInitials.append(myName.charAt(i)); } } System.out.println("My initials are: " + myInitials); } }
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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)) { dest.append(c); } } return dest.toString(); } protected static String sort(String string) { char[] charArray = string.toCharArray(); 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(); } }