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Assignment 1 Solution
Purpose:
To gain experience with
Java
Fixed length arrays
In this assignment you will create a complete program that uses classes to store, search, sort, remove, and filter country data. The two major tasks are outlined below.
Provided With:
You are given a file called Assignment1.java that contains a main method. Use this class to run the code you write. Your code must work with this file; you cannot alter this file as a means of making your code work. The marker will use a file similar to this to test the functionality of your code.
You are also provided two files called ThingToWriteFile.java and ThingToReadFile.java. These classes are provided to make fileIO easier. Have a look at the code to understand how to use these objects.
Two text files are included. One contains the country information (data.txt) and the other contains the country/continent information (continent.txt). NOTE: Both of these files have a header line!
On the last page of this assignment you are provided with an example output. Reference this for text formatting.
You may assume all data is correct and that there are no errors in the data files (don’t worry about exceptions, or validating inputs, etc.).
Stuff To Do:
Implement a Country class:
The purpose of this object is to represent a country. This object will store some important information about the country and will have a small number of simple methods.
This class will contain variables for the country name, population, area, and continent in which it exists.
You will need to write a constructor for the object. This constructor should take a name, population, area, and continent as parameters.
Write getter methods for the four instance variables (getName, etc.).
Write a method called getPopDensity to return the country’s population density (population/area).
Write a single setter method for the population instance variable (setPopulation).
Write a method called writeToFile which takes a ThingToWriteFile object as a parameter. This method must write some country details to the provided ThingToWriteFile object provided. Below is an example of how to print the details to file (commas are important):
NAME, CONTINENT, POPULATION, POPULATION DENSITY
Ex: Canada, North America, 34207000, 3.428881310807587
Write a method printCountryDetails that prints some country details to the user:
NAME is located in CONTINENT has a population of POPULATION an area of AREA and has a population density of GETPOPDENSITY
Ex: Canada is located in North America has a population of 34207000, an area of 9976140.0, and has a population density of 3.428881310807587
Write a toString method which simply returns a string in this format (include a new line character at the end):
NAME in CONTINENT
Canada in North America
Test all your classes and methods before moving to the next section. Feel free to create other helper methods if necessary.
Implement a CountryCatalogue class:
The class should have a few important instance variables:
A final int called DEFAULT_SIZE which is equal to 5. This variable will be used when the catalogue array is instantiated.
A final int called NOT_FOUND which is equal to -1. This will be used as a flag for some of our methods.
A country array called catalogue which will store a bunch of countries.
An int which stores the number of countries currently in the catalogue
A set of <Strings called continents. This set will store the continents. Don’t know how to create a set in java? Look up the java docs, or just Google “Java sets”. This set will make one of the below methods easier to implement.
A <String, String Map (dictionary) called cDict which will map a country name to a continent. This will be used to make some of the below methods easier to implement.
Write the constructor (this gets a little complex). The constructor should:
Take two strings as parameters. One string will be the name of the file containing the country information, and the other will be the name of the file containing the continent information.
Instantiate the instance variables.
Read the country file (with a ThingToReadFile object) one line at a time, parse the text, create a Country object based on the text, and then add the Country to the catalogue with a method called addCatalogue (more on this below). Be sure to close the file when done.
Read the continent file (with a ThingToReadFile object) one line at a time, parse the text, and then add the details to cDict and continents. Be sure to close the file when done.
Write a private method called addCatalogue which takes a country as a parameter. This method only adds the provided country to the catalogue. However, we may have a problem, the catalogue may be full! For this method, don’t worry about adding duplicate countries.
Write a private method called expandCapacity that will double the size of the catalogue array. This method can be called by addCatalogue if there is no more room for a new county to be added.
Write a method called addCountry which takes a country as a parameter. This method should add the provided country object to the catalogue and update the continents set and cDict map. This method can call addCatalogue. For this method, don’t worry about adding duplicate countries.
Write a method getCountry that takes an index as a parameter and returns a Country object from the indexed location in the catalogue. This method should return null if the index provided is inadmissible.
Write a method printCountryCatalogue which simply calls the toString method for each Country currently in the catalogue instance variable.
Write a method filterCountriesByContinent which will print out all the countries from a specified continent (just use the county’s toString method). This method will take a String representing the continent we want the countries from.
Write a method searchCatalogue which takes a String of a name of a country we want to find. This method will return an int representing the index of the found country in catalogue. If the item is not in the list, return NOT_FOUND. Print some sort of notification to the user if the country was not found.
Write a method removeCountry which takes a String of a name of a country we want to remove from the catalogue. This method can use searchCatalogue. Print some notification to the user whether or not the item was successfully removed or not.
Write a method setPopulationOfACountry which takes a String representing the name of a country we want to alter and an int representing the new population. This method can call searchCatalogue. Print some notification to the user whether or not the item was successfully altered or not.
Write a method saveCountryCatalogue which will write the catalogue’s county’s to file. This method takes a String representing the name of the file we want to save the details to. This method can simply call the Country’s writeToFile method.
Write a method findCountryWithLargestPop which will return the index location of the country with the largest population currently in the catalogue.
Write a method findCountryWithSmallestArea which will return the index location of the country with the smallest area currently in the catalogue.
Write a method printCountriesFilterDensity which prints out some country details if the country lies within some specified population density range. This method takes two integers specifying the range inclusively (low and high). This method will have some additional bookkeeping. See the example output provided below for a demonstration of how this output should look.
Write a method findMostPopulousContinent which prints out the continent, and the total population of that continent (based only on the countries in the catalogue) of the continent with the largest population. See the example output provided below for a demonstration of how this output should look.
Test all your classes and methods. Feel free to create other helper methods if necessary.
FAQ:
Q: How do I compare strings? Can I just use == ?
A: NO! DO NOT USE ==!!!!!!!!!!! Comparing Strings in Java is… very weird actually (and actually the subject of some debate). Use a method called equals instead. For example:
SomeString.equals(SomeOtherString) will be true if the Strings are the same.
Q: Why can’t I use == then?
A: It’s complicated. I’ll go into this later in the course.
Q: I don’t know how to do X?
A: Try going to www.google.ca and then typing X into the big text box.
Q: How do we use Maps (dictionaries) in Java?
A: The idea is similar to python, but there are some Java-isms here. First, check out the java docs for Maps (https://docs.oracle.com/javase/7/docs/api/java/util/Map.html). You’ll need to import the library they are defined in. Also, try looking up examples of people using them. Instantiating them is a little weird (more details on this later in the course, for now you’ll have to just type the magic code) (HINT for instantiation: hashmap). Iterating through them is different too; try Googling how to iterate through a map in java.
Q: How do we use Sets in Java?
A: Basically exactly the same answer above, but the java docs are different (https://docs.oracle.com/javase/7/docs/api/java/util/Set.html)
Q: How do I parse a String in Java?
A: Try looking up “splitting a string in java” with Google.
Q: I swear I did everything right, but for some reason my files won’t open!
A: This isn’t uncommon.
If you’re using eclipse, try putting the .txt files in the project directory (the same folder containing the bin folder, src folder.
If you’re running from command line, try putting the files in the src folder.
Non-functional Specifications:
Include brief comments in your code identifying yourself, describing the program, and describing key portions of the code.
Assignments are to be done individually and must be your own work. Software may be used to detect cheating.
Use Java coding conventions and good programming techniques, for example:
Meaningful variable names
Conventions for naming variables and constants
Use of constants where appropriate
Readability: indentation, white space, consistency
Submit Country.java and CountryCatalogue.java. to OWL. Make sure you attach your .java files to your assignment; DO NOT put the code inline in the textbox. DO NOT SUBMIT YOUR .class FILES. IF YOU
DO THIS, AND DO NOT ATTACH YOUR .java FILES, YOU WILL RECEIVE A MARK OF ZERO!
What You Will Be Marked On:
Functional specifications:
Does the program behave according to specifications? Does it run with the main program provided?
Are your classes created properly?
Are you using appropriate data structures? Is the output according to specifications?
Non-functional specifications: as described above
Assignment submission: via OWL assignment submission
Example output from provided Main.java:
Canada is located in North America has a population of 34207000, an area of 9976140.0, and has a population density of 3.428881310807587
Target country not in catalogue.
England is located in Europe has a population of 54316600, an area of 130279.0, and has a population density of 416.9252143476692
Country "England" removed successfully.
Target country not in catalogue.
Country Catalogue:
China in Asia
United States of America in North America
Brazil in South America
Japan in Asia
Canada in North America
Indonesia in Asia
Nigeria in Africa
Mexico in North America
Egypt in Africa
France in Europe
Italy in Europe
South Africa in Africa
South Korea in Asia
Colombia in South America
Zambia in Africa
Ghana in Africa
Country with the largest population: China is located in Asia has a population of 1339190000, an area of 9596960.0, and has a population density of 139.5431469965489
Country with the smallest area: South Korea is located in Asia has a population of 50503933, an area of 98076.92, and has a population density of 514.9420781158299
Countries in North America:
United States of America
Canada
Mexico
Countries with a population density between 0 and 25:
Brazil in South America
has a population density of 22.716728745947616.
Canada in North America
has a population density of 3.428881310807587.
Ghana in Africa
has a population density of 0.21889705799512446. Continent with the largest population: Asia, with 1777655033,
