The main goals for this lab are for you to get more comfortable designing classes and working with objects.
This lab is a paired programming assignment. What exactly does that mean? You will be working in pairs on the CS lab computers. Each pair will be working on one computer. One person will be the driver and the other person will be the navigator. Here is the rule: the driver controlls the lab computer, but the driver can only type what the navigator tells them to type. For this to work well, each pair should be constantly talking among themselves. After each problem, you will switch roles, the navigator will become the driver and the driver will become the navigator.
Partners You must work with your partner from last weekYou will be working together for one more week.
Before leaving the lab, make sure you fill out the attendance sheet and go through your answers with a TA or instructor. You will not get full credit otherwise.
In this lab you will be designing a student’s course schedule. You will be creating two files, Course.java and Schedule.java. By the end of this lab, you will have written a program to read in a file containing a students schedule, parse the file, and create Course objects and a schedule.
TODO: Download the file schedule.csv from the course website. Run wget https://cs.brynmawr.edu/cs113/website/labs/lab07/schedule.csv to download the file.
Question: 2.1: In the space below, write down what properties a college course has?
Question: 2.2: Look at the file called schedule.csv. Each line there represents another course. According to that file, a course has 5 properties. In the space below, write down what those properties are?
Now that we know a course will have 5 properties, we can begin creating Course.java.
First, in the begining of the class (so right below public class Course.java), create these 5 instance variables. Make sure the access modifiers for the instance variables are set so that access to the variables is limited to just this object.
Hint: Look at page 189 of the textbook for an example.
Next, create an empty constructor. Remember, an empty constructor does not take in any parameters. The role of the empty constructor is to create an instance of the class where all the instance variables are set to the defaults.
THerefore, in your empty constructor, initialize values for all the instance variables.
Next, create a value constructor that takes in 5 parameters and sets the instance variables to the values in the parameters.
Make sure to use the same variables names for your parameters as the instance variables. In this case, dont forget to use a special keyword that allows you to access the instance variables when shadowing occurs.
Hint: Look at section 11.3 of the textbook
Next, for each of the instance variables, create a corresponding getter and setter method.
Testing: In the main method, create a new Course object, then use the getters to test that the new Course object contains all the values specified when you create the new Course object.
DO NOT GO ON IN THIS LAB WITHOUT SHOWING AN INSTRUCTOR YOUR ANSWERS SO FAR. OTHERWISE YOU WILL NOT GET FULL POINTS FOR THIS LAB!
MAKE SURE YOU WROTE OUT ALL OF YOUR ANSWERS TO ALL OF THE QUESTIONS ABOVE.
Dont forget that every class needs to have a toString() method that returns a string representation of the object. Now implement your toString() method.
Then, in main, call toString() on your object and print out the object.
If we want to check if two objects are equal to each other, recall that we cannot use ==.
Question 2.5.1: What does == compare?
Hint: Look at section 11.7 of the textbook
Instead, we can use the equals method to check if two objects are equivalent.
Now, create an instance method called equals() that takes in another Course object as a parameter. The method should return true if the values in the objects’ instance variables are equivalent.
Finally, test equals() in your main method. The easiest way to test this is to create two empty objects (using the empty constructor) and then compare them.
DO NOT GO ON IN THIS LAB WITHOUT SHOWING AN INSTRUCTOR YOUR ANSWERS SO FAR. OTHERWISE YOU WILL NOT GET FULL POINTS FOR THIS LAB!
MAKE SURE YOU WROTE OUT ALL OF YOUR ANSWERS TO ALL OF THE QUESTIONS ABOVE.
Now that we implemented a Course class, we can implement a Schedule class.
Create an empty file called Schedule.java
Question 3.1.1: Besides for a list of Courses, what else might a Schedule have?
Next, at the top of the class, declare your instance variables, including an array of Courses (dont initialize it).
Next, create a Constructor method. The parameters in the constructor should be values for the instance variables. One of the parameters should indicate how
many Courses are in the schedule.
Question 3.2.1: How will you use the number of Courses in the schedule in your constructor?
Now, implement the constructor
Implement a toString() method that returns a string representation of the schedule.
In the string representation, Id recommend the string first containing information about the schedule, e.g. the name of the schedule/student, the semester, or whatever instance variables you can up with above. Then, I’d have one new line in the string for each course.
Recall: you can create a string representation for each course by using the course object’s toString() method.
Next, we need a way to add a course to our schedule.
Implement an instance method called addCourse() that takes in a course as a parameter and adds the course to the end of the list of courses. For example, if there are no courses in the list, then we would add a new course to the first slot of the array. If there are 3 courses, we would add the new course to the 4th slot of the array.
If there is no more room for a course, the method should not override any existing courses. Instead the method should print out a message saying that it cant add the new course and then return false.
Based on this last instruction, what do you think the return type of addCourse() should be? Additionally, what should the method return after successfully adding a course.
Finally, in main(), test addCourse.
DO NOT GO ON IN THIS LAB WITHOUT SHOWING AN INSTRUCTOR YOUR ANSWERS SO FAR. OTHERWISE YOU WILL NOT GET FULL POINTS FOR THIS LAB!
MAKE SURE YOU WROTE OUT ALL OF YOUR ANSWERS TO ALL OF THE QUESTIONS ABOVE.
If you recall from the begining of the lab, we provided a file that contains a list of courses.
Look at any of the lines in schedule.csv.
Question 3.5.1: Look closely, what character are we using to seperate the different properties of a course?
That means, we can use the .split() method to convert each row into an array of Strings.
Before parsing the file, I’d recommend copying one line from the file and storing it in a string. Next, create a static method called createCourseFromLine() that takes in a string as a parameter and creates a new course object from that string.
Hint: Since some of a Course’s instance variables are not Strings, your method will probably need to convert some Strings to other types.
Now we can create a new instance method called addCoursesFromFile(). This method’s parameter should be a String that indicates the file name that contains the schedule.
The method should use the File class to create a new File object and then use a Scanner object to iterate through the file. When iterating through the file, at each line the method should call createCourseFromLine() and then addCourse().
Finally, in the main method, create a new Schedule object. Then call addCoursesFromFile() to add the courses. Finally, print out the Schedule object to confirm that everything works.
Congrats, you have completed the lab!
In today’s lab we covered designing classes and working with objects. You gained more practice with splitting Strings and working with files.
Before leaving, make sure your TA/instructor have signed you out of the lab. If you finish the lab early, you are free to go.