CS111 Lab 8 - StringList Methods

In this lab, you will get experience writing methods that manipulate lists. Rather than using the lists of integers introduced in lecture, in this lab we will be using lists of strings since these will be used in Problem Set 7. The contract for the StringList class is almost identical to the contract for the IntList class the only difference is that the StringList methods use the types String and StringList whereever the IntList methods use the types int and IntList.

Begin this assignment by downloading the file /cs111/download/lab8_programs. Below, you are asked to write several class methods that manipulate string lists. You should write the definitions of each of these class methods in the class LabOps within the file LabOps.java. To test your class methods, you should add testing statements to the main method in the LabOps class. The LabOps class is executed as an application, not as an applet. You need to be careful to quit out of any previous MRJ applications for the class before executing the class again.

Your task is to write and test the class methods described below. Write your methods one-by-one. When you have written a method, write several test statements in main to make sure that your method works in all cases. Don't forget to test your methods on empty lists (if applicable).

Here are the methods that you need to write:

public static StringList mapPluralize (StringList L)
Assuming that L is a list of nouns, returns a new list with the plurals of each of the nouns. The nouns are pluralized by adding the suffix "s". For instance, the plural of "cat" is "cats" and the plural of "mouse" is "mouses" (this simple-minded pluralizer doesn't know about special cases like "mice").
Examples:
mapPluralize(fromString("[dog,cat,mouse]")) returns the string list [dogs,cats,mouses].
mapPluralize(fromString("[]")) returns the string list [].
public static StringList mapUpperCase (StringList L)
Returns a new list that converts every string in the given list to upper case.
Examples:
mapUpperCase(fromString("[dog,cat,mouse]")) returns the string list [DOG,CAT,MOUSE].
mapUpperCase(fromString("[]")) returns the string list [].
Note: Use the toUppercase() instance method from the String class to convert individual strings.
public static boolean isMember (String s, StringList L)
Returns true if s is an element of L, and returns false otherwise.
Examples:
isMember("dog", fromString("[dog,cat,goat]")) returns true.
isMember("cat", fromString("[dog,cat,goat]")) returns true.
isMember("goat", fromString("[dog,cat,goat]")) returns true.
isMember("tiger", fromString("[dog,cat,goat]")) returns false.
isMember("at", fromString("[dog,cat,goat]")) returns false.
isMember("go", fromString("[dog,cat,goat]")) returns false.
isMember("dog", fromString("[]")) returns false.
Note: Make sure that the method handles the empty list!
public static StringList explode (String s)
Returns a list of single-character strings formed out of the characters of the given string s.
Examples:
explode("computer") returns the string list [c,o,m,p,u,t,e,r].
explode("") returns the string list [].
Notes: The LabOps class contains two helper methods that are useful for defining explode:
1. public static String first (String s)
  Returns a string consisting of the first character of s. For example, first("computer") returns the string "c".
2. public static String butFirst (String s)
  Returns a string consisting of all but the first character of s. For example, butFirst("computer") returns the string "omputer".
public static String implode (StringList L)
Returns a string that is the result of concatenating all the strings in L in order.
Examples:
implode(fromString("[dog,cat,mouse]")) returns the string "dogcatmouse".
implode(fromString("[lists, are, fun]")) returns the string "lists are fun".
implode(fromString("[]")) returns the string "".
public static StringList filterMatches (String s, StringList L)
Returns the list of strings in L that contain s as a substring.
Examples:
filterMatches("com", fromString("[computer,program,incomparable,intercom,Java]")) returns the string list [computer,incomparable,intercom]
filterMatches("com", fromString("[cat,dog,mouse]")) returns the string list []
filterMatches("com", fromString("[]")) returns the string list []
Note: To test if one string is a substring of another, you should use the indexOf() instance method from the String class. It works as follows. Let s1 and s2 be two strings. Then s1.indexOf(s2) returns the index of the first occurrence of s2 in s1, or -1 if it does not occur at all. For example, if s1 is the string "Hi there", then:
- s1.indexOf("Hi") returns 0
- s1.indexOf("there") returns 3
- s1.indexOf("e") returns 5
- s1.indexOf("bye") returns -1
public static StringList insert (String s, StringList L)
Assume that L is an n-element list of strings sorted in alphabetical order. Returns a new (n+1)-element list of alphabetically sorted strings that contains s in addition to all the elements of L.
Examples:
insert("dog", fromString("[cat,goat,lion]")) returns the string list [cat,dog,goat,lion].
insert("ant", fromString("[cat,goat,lion]")) returns the string list [ant,cat,goat,lion].
insert("tiger", fromString("[cat,goat,lion]")) returns the string list [cat,goat,lion,tiger].
insert("goat", fromString("[cat,goat,lion]")) returns the string list [cat,goat,goat,lion].
Note: In Java, two strings are compared via the compareTo() instance method of the String class. It works as follows. Let s1 and s2 be two strings. Then s1.compareTo(s2)
- returns -1 if s1 comes before s2 in alphabetical order;
- returns 0 if s1 and s2 are equal strings;
- returns 1 if s1 comes after s2 in alphabetical order.
For example:
- "cat".compareTo("dog") returns -1;
- "cat".compareTo("cat") returns 0;
- "cat".compareTo("ant") returns 1.
public static StringList insertionSort (StringList L)
Returns a new list that contains all the elements of L in alphabetical order.
Examples:
insertionSort(fromString("[lion,dog,cat,ant,goat]")) returns the string list [ant,cat,dog,goat,lion].
insertionSort(fromString("[Time,flies,like,a,banana]")) returns the string list [Time,a,banana,flies,like].
insertionSort(fromString("[]")) returns the string list [].
Notes:
- Capitalized words (such as "Time") are considered to alphabetically precede uncapitalized words (such as "banana").
- Your insertionSort method should work by using the insert method you defined above to insert the head of the list into the result of recursively sorting the tail of the list.