CMPU 102 - Assignment 3 - February 23rd, 2017

In this lab you will practice writing a class hierarchy in Java to produce lists as you did in CMPU 101. You are encouraged to use NetBeans on this assignment, but you may use DrJava if you want. Please read through Part I of the lab before starting to code.  You can use either the System.out.println() calls given in TestIList.java, or you can convert these to JOptionPane showMessageDialog calls if you prefer. 

Part I: Structural Recursion Using an Interface

1. Download the zipped starter project called Assign3 from the course web page.
   
   
2. Uncompress the Assign3 project in your cs102 directory.
   
   
3. Launch NetBeans and open the project named Assign3. 
   
   
4. The project includes the following Java source files: TestIList.java, IList.java, MTList.java, and ConsList.java. The main method is in the TestIList class.
   
   
5. The file called  IList.java contains the method stubs that must be written in any class that implements IList.  There should be 2 method stubs that are not commented out.  These were shown in class on 2/22/17 and are the length method and the sum method.  The length and sum methods are also written in the MTList and ConsList classes, so you should be able to run the TestIList.java file right away.
   
   The IList file also contains commented out method stubs that you can uncomment, one at a time, as you implement each method body in the classes that implement IList.
   
   
6. When you run the TestIList class for the first time, you should see output that looks somewhat like this (with different random numbers):
   
   run:
   The list of random numbers: 42 12 18 31 69 82 59 28 18 28 81 65 84 11 31 46 96 52 90 9
   
   The length of the list is 20
   
   The sum of the numbers in the list is 952
   
   BUILD SUCCESSFUL (total time: 0 seconds)
   
   
   
   Note how the random numbers are generated in the generateNumber method of the TestIList class. Math.random() outputs a double in the range 0 to 1, (not including 1). You can multiply the result by the range of numbers you want to produce, adding 1 to make the returned number in the range 1...100. The number returned by calling Math.random() multiplied by 100 and adding one is then cast to an int.
    

Part II: Implementing new methods of the IList interface

1. Uncomment the line public IList doubleEach();  in the IList interface and then implement the method in both the MTList and ConsList classes.  This method should return the IList that contains all the numbers in the list it is called on, with each number multiplied by 2.  It may help to write each MTList method before you write each Conslist method.
   
   After implementing doubleEach() in both subtypes of IList, uncomment the lines to test doubleEach in the TestIList class.
   
   
2. Uncomment the line public IList onlyEvens();  in the IList interface and then implement the method in both the MTList and ConsList classes.  This method should return the IList that contains only the even numbers in the list it is called on.
   
   After implementing onlyEvens() in both subtypes of IList, uncomment the lines to test onlyEvens in the TestIList class. When you run TestIList after adding the implementations of the doubleEach and onlyEvens method, the output should look something like this:
   

Part III: Implementing the remaining methods of the IList interface

1. First, it's easy to sort an empty list, and it's easy to insert an element into the empty list. Think about what the result of calling sort() and insert(int num) would be for an empty list, and implement both of these methods for class MTList.
   
   
2. Next, it's easy to sort a constructed list (ConsList), if you think about it: insert the first element into the sorted rest of the list. Hint: you will implement insert(int num) next, but while implementing sort(), assume insert(int num) is already implemented.
   
   
3. Finally, inserting an element into a sorted list is easy, too: compare the element to be inserted with the first element of the list. It either belongs in front of it, or after it--return the appropriate newly constructed list.
   
   
4. After implementing sort() and insert(int num) in both subtypes of IList, uncomment the lines to test the sort method in the TestIList class.
   
   
5. Save and  run your project. Your output should look something like that shown below.  Here is a sample output:
   
   run:
   The list of random numbers: 7 85 17 14 10 29 45 49 23 55 42 12 67 96 85 98 40 77 52 9
   
   The length of the list is 20
   
   The sum of the numbers in the list is 912
   
   The doubled numbers in the random list are 14 170 34 28 20 58 90 98 46 110 84 24 134 192 170 196 80 154 104 18
   
   The even numbers in the random list are 14 10 42 12 96 98 40 52
   
   The random list is
   7 85 17 14 10 29 45 49 23 55 42 12 67 96 85 98 40 77 52 9
   
   The sorted list is
   7 9 10 12 14 17 23 29 40 42 45 49 52 55 67 77 85 85 96 98
   
   BUILD SUCCESSFUL (total time: 0 seconds)
   

Part IV Submitting Your Work

Compress your NetBeans Project folder and submit it at the "Assignment 3 submission link" on the course Moodle page.