Lab 1: Introduction to Eclipse and Simple Data Definitions
Goals: The goals of this lab are to get familiar with our work environment: the Eclipse IDE, the handin-server submission process, the basics of running a program in Java, and program testing framework.
The second part of the lab will focus on practicing data definitions and examples in Java.
Video Lessons
1.1 Khoury Accounts
You will use Bottlenose to work on your homework sets, to keep track of revisions, and to submit your homework. You will need a Khoury account to use Bottlenose so please go here to apply for an account if you don’t already have one.
Important: if you have had a Khoury account in the past, but are not a Khoury student and your account has been deactivated due to inactivity, do not apply for a new account. Instead, send an email to khoury-systems at northeastern dot edu explaining that you’re registered for CS2510, that your account has been disabled, and provide your Khoury username and your NUID in the email. You will not likely be able to log in until the Systems team has a chance to process your account, so be patient.
1.2 Introduction
We start with designing data - designing classes of data that are connected to each other in a systematic way, showing that the Design recipe for Data Definitions can be used virually without change in a completely different language than we have used in the first part.
The programs we provide give you examples of the progressively more complex data (class) definitions, and illustrate the design of methods for these class hierarchies.
1.3 Eclipse IDE
Eclipse is an integrated (program) development environment used by many professional Java programmers (as well as programmers using other programming languages). It is an Open Source product, which means anyone can use it freely and anyone can contribute to its development.
The environment provides an editor, allows you to organize your work into several files that together comprise a project, and has a compiler so you can run your programs. Several projects form a workspace. You can probably keep all the work till the end of the semester in one workspace, with one project for each programming problem or a lab problem.
There are several steps to getting started:
Learn to set up your workspace and launch an Eclipse project.
Learn to manage your files and save your work.
Learn how to edit your Java programs and run them, using our tester library.
Learn to set up your workspace.
IF YOU ARE USING A KHOURY MACHINE:
Start working on two adjacent computers, so that you can use one for looking at the documentation and the other one to do the work. Use your Khoury username and password to log in to the machine.
Create a workspace folder in your home directory where you will keep all your Java files. This should be in
z:\EclipseWorkspace
Note that z: is the drive that Windows binds your UNIX home directory, and you can name it something else if you really want to.
Next, set up another folder in your home directory where you will keep all your Java library files. This should be in
z:\EclipseJars
We will refer to these two folders as EclipseWorkspace and EclipseJars. Make sure the two folders EclipseWorkspace and EclipseJars are subfolders of the same folder.
Start the Eclipse application.
DO NOT check the box that asks if you want to make this the default workspace for Eclipse if you are working on the lab computer. If you are working at home or using your laptop, you may want to make the selected workspace to be your default. Select your previously created EclipseWorkspace folder as your workspace.
IF YOU ARE USING YOUR OWN MACHINE:
First, install the Java Development Kit (JDK): download Java 11 from https://www.oracle.com/java/technologies/downloads/#java11 appropriate for your machine, and install it. Note that you might be asked to create an Oracle account. If so, please create one. When you click on the download link, login with your account you just created and the download should start. Make sure you choose the JDK option, and not merely the JRE: the latter only enables you to run Java programs, but the development kit lets you develop them.
Do not use any version higher than 11. The submission server does not support higher versions, so you may have some problems when you submit.
Next, download Eclipse from https://www.eclipse.org/downloads/ – the standard Eclipse IDE release is fine, and the Eclipse site should detect your computer’s operating system appropriately. When installing it, select Eclipse IDE for Java Developers, for this is what you are becoming!
Before opening the programming (while it installs), follow the instructions above, replacing the reference to Z:\ with whatever folder on your computer is convenient for you.
The First Project
Right click the following two libraries and select "Save link as..." Save them to your EclipseJars folder.
The libraries you will need are:
Create a project.
Back in Eclipse, in the File menu select New then Java Project. Name the project Lab1. In the window that appears in the Project layout under JRE, make sure "Use an execution environment JRE" is selected, and make sure version 11 is selected, if not already selected by default (it might say something like "JavaSE-11"). If it you don’t see Java version 11 in the drop down list, it might mean that you skipped the step above asking you to instal Java version 11 from the Oracle website.
Then under "Project layout" make sure you select Create separate folders for sources and class files.
Also, make sure "Add project to working sets" is unchecked.
Click Next. If you see the option to make a module file, please uncheck it (it might say something like "create module-info.java file"). Select Finish, as the other defaults should be fine. If you see a tab with "Welcome" in the title that has a lot of options, exit out of the tab with the white x.
Make the libraries available to the new project.
Highlight your Project in the Package Explorer pane, then right-click it and select "Properties". In the list on the left, select the Java Build Path, then select the Libraries tab. NOTE: If you are using Java 9 or higher, you should see two options in the main area of the form: "Modulepath" and "Classpath". Make sure that you have clicked on "Classpath" to select it. If you do not see these two options, just ignore this step.
Note: If the pane is not visible, go to Window menu, select Show View... then Package Explorer. You should also select Show View... Outline.
On the right click on Add External JARs...
The file chooser window will be shown. Navigate to your EclipseJars folder and select all jar files you have downloaded.
Hit Apply and Close.
Add the Shapes.java file to your project.
Download the file Shapes.java to a temporary directory or the desktop. You might have to click on the file which will open it into a separate tab for viewing. Then, right click and select "Save as". Make sure the file ends in .java and not .java.txt.
In Eclipse highlight the src box under the Lab1 in the Package Explorer pane.
In the File menu select Import....
Choose the General tab, within that File System and click on Next.
Browse to the temporary directory that contains your Shapes.java file and click "Open".
Click on the directory on the left, then select the Shapes.java file in the right pane and once you have checked the "Into folder" is Lab1/src, hit Finish.
View the file Shapes.java.
Click on the src block under Lab1 in the Package Explorer pane. It will reveal default package block.
Click on the default package block. It will reveal Shapes.java.
Double click on Shapes.java. The file should open in the main pane of Eclipse.
You can now edit it in the usual way. Notice that the Outline pane lists all classes defined in this file as well as all fields and methods. It is almost as if someone was building our templates for us.
Adjust the Eclipse settings.
The Code style section explains how to configure Eclipse to only use spaces instead of tabs, and how to set the editor to show you the line numbers for all lines in the code. If you have trouble, ask a TA for help.
Set up the run configuration and run the program.
Highlight Lab1 in the Package Explorer pane.
In the Run menu select Run Configurations....
In the list on the left, make sure "Java Application" is selected. Then, in the top left corner of the inner pane click on the leftmost item. (When you mouse over it should show New launch configuration.)
Select the name for this configuration - usually the same as the name of your project.
In the Main class: click on Search....
Among Matching items select Main - tester and hit OK.
Click on the tab (x)= Arguments. In the Program arguments text field enter ExamplesShapes.
Later, when you define your own program, you will use the class name of your Examples... class instead of ExamplesShapes.
At the bottom of the Run Configurations select Apply then Run.
Next time you want to run the same project, make sure Shapes.java is shown in the main pane (and is currently selected), then hit the green circle with the white triangle on the top left side of the main menu.
Interface? Implements?
As we fondly remember from CS2500, one of our favorite types of data is union data: enumerations, itemizations, etc. To define union data in Java, we define that union as an interface and say each branch of the data implements the interface. Read the code in your shapes file: you’ll notice the IShape interface is defined at the top, and that each class implements it. In the examples section, the examples are given the type of the interface, and are created with the constructor of the specific class. Follow suit when defining your own examples.
Simple Data Definitions
Problem 1
Here is a data definition in DrRacket:
;; to represent a person ;; A Person is (make-person String Number String) (define-struct person [name age gender]) (define tim (make-person "Tim" 23 "Male")) (define kate (make-person "Kate" 22 "Female")) (define rebecca (make-person "Rebecca" 31 "Non-binary"))
Draw the class diagram that represents this data.
Define the class Person that implements this data definition and the class ExamplesPerson that contains the examples defined above. You should do this in a new Person.java file. Right click the default package under Lab1 and select New > File. Name it Person.java.
Run your program to make sure it works.
Data Definitions with Containment
Problem 2
Modify your data definitions so that for each person we also record the person’s address. For each person’s address we only record the city and the state; each of these should be its own field. Create an Address class to contain the address information, then modify the Person data definition to include an Address.
Draw the class diagram for this data definition
Define Java classes that represent this data definition.
Tim lives in Boston, MA, Kate lives in Warwick, RI, and Rebecca lives in Nashua, NH.
Make examples of these data and add two more people.
Data Definitions for Unions of Data
Problem 3
A deli menu includes soups, salads, and sandwiches. Every item has a name and a price (in cents - so we have whole numbers only).
For each soup and salad we note whether it is vegetarian or not.
Salads also specify the name of any dressing being used.
For a sandwich we note the kind of bread, and two fillings (e.g peanut butter and jelly; or ham and cheese). Assume that every sandwich will have two fillings, and ignore extras (mayo, mustard, tomatoes, lettuce, etc.)
Define classes to represent each of these kinds of menu items. Think carefully about what type each field of each class should be. Do you need to define any interfaces? Construct at least two examples each of soups, salads, and sandwiches.
Self-Referential Data
The HtDP book includes the data definition for Ancestor Trees:
;; An Ancestor Tree (AT) is one of ;; -- 'unknown ;; -- (make-tree Person AT AT) ;; A Person is defined as above
Convert this data definition into Java classes and interfaces. What options do you have for how to translate this into Java? Make examples of ancestor trees that in at least one branch cover at least three generations.
Hint: We actually cover this in Lecture2 all the way at the bottom of the page : ). Try to do it without looking at Lecture2 and afterwards check your answer with the lecture notes.