On this page:
1.1 Khoury Accounts
1.2 Introduction
1.3 Eclipse IDE
Learn to set up your workspace.
The First Project
Set up the run configuration and run the program.
Interface? Implements?
Making examples
Simple Data Definitions
Data Definitions with Containment
Data Definitions for Unions of Data
Self-Referential Data
8.5

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.

Submission: Make sure to complete the Lab 1 questions in handins before you leave lab today.

Related files:
  tester.jar     javalib.jar     Shapes.java  

1.1 Khoury Accounts

You will use the Handin Server to work on your homework sets, to keep track of revisions, and to submit your homework. You will need a Khoury account to use the Handin Server so please go here to apply for an account if you don’t already have one.

Important: if you have had a Khoury (or CCS) 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.
The First Project
Set up the run configuration and run the program.
Interface? Implements?

As we fondly remember from CS2500, one of our favorite types of data is union data: enumerations, itemizations, etc. This is covered in Lecture 2, so you can skip to Problem 1 below if you have not read Lecture 2 yet.

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.

Making examples

Add examples of shapes found in the following image (ignore the colors, and note you do not actually have to draw the shapes):

Run your examples class with the tester library to make sure it works.

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.

Problem 3 We want to define events which have a title, date, location and host. What types of data should you use for each of these fields? A date should have a day, month and year. A host should be a Person.

You should do this problem in a new Event.java file. Right click the default package under Lab1 and select New > File. Name it Event.java.

Data Definitions for Unions of Data

Problems 4 and 5 concern material found in Lecture 2. You can attempt them if you like.

Problem 4

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

Problem 5

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.