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Inner Classes

Objectives

  • Use member classes, local classes, and anonymous classes for sorting and filtering lists.

Overview

The President class includes appropriate fields, getters and setters, and a constructor that takes all fields. It also implements Comparable<President>, overriding compareTo to set the natural sort order using term number.

The file resources/presidents.tsv consists of records with tab-separated fields.

  1. Copy PresidentAppDates.java, naming the new copy PresidentAppInnerClasses.java.

  2. Make sure the new class's main instantiates a PresidentAppInnerClasses, not PresidentAppDates.

This class has a method that parses the file, creating an ArrayList<President>. Its printPresidents method takes List<President> and prints it using President's toString.

Tasks

Sorting

  1. Create a method that returns a list of presidents sorted by party and term number. Use a member class that implements Comparator<President>. Pass the original list to this method, and print the resulting list.

  2. Create a method that returns a list of presidents sorted by the reason they left office, then by term number. Use a local class for the comparator. Pass the original list to this method, and print the resulting list.

  3. Create a method that returns a list of presidents sorted by last name. Use an anonymous class for the comparator. Pass the original list to this method, and print the resulting list.

Filtering

The PresidentMatcher interface defines the boolean method matches, which takes a string and a President reference. The PresidentPartyMatcher example returns true if the string matches the president's party (ignoring case).

In PresidentAppInnerClasses, the filter method takes a String and a PresidentMatcher implementation, returning a list containing presidents for which the matcher's matches method returns true.

  1. Use PresidentPartyMatcher and the filter method to print a list of Whig presidents.

  2. Define a member class that implements PresidentMatcher, with matches returning true if the president's first name starts with the string passed in.

  3. Use a local (in start) implementation of PresidentMatcher that matches presidents based on why they left office. Print the list of presidents who left when their term ended.

  4. Use filter() and anonymous PresidentMatcher implementations to print lists of Presidents:

  5. Whose last names start with "C".
  6. Whose party contains the string "Democrat".
  7. Who died in office
  8. Who won only a single election.
  9. Whose terms started in the 19th century.

Stretch Goals

  1. If you haven't already, create a method that takes a list of presidents and writes it as tab-separated values to a file.

  2. Records should be formatted so the existing code would be able to read and parse the records.

  3. When testing, be careful NOT to use resources/presidents.tsv as the output file!

  4. Pass filtered lists and filenames to this method to save files with the presidents from each party.

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