Computer Science I

Lab 1.0 - Introduction

Java Version

School of Computing
College of Engineering
University of Nebraska-Lincoln

This lab introduces you to your programming environment and the software development workflow and handin/grading process used by this course.

Prior to Lab

In each lab there may be pre-lab activities that you are required to complete prior to attending lab. Failure to do so may mean that you are not prepared to complete the lab.

1. For this lab, you'll need to sign up with GitHub, a website that hosts software repositories using git (a distributed version control system). With GitHub you'll be able to store, manage and backup your source code. Git is an essential software development tool that you'll want to fully utilize.

   Go to https://github.com and sign up if you don't have an account already.

2. Accept the invite that your instructor sent out from codepost.io and be sure you can sign in. Graders will provide line-by-line feedback on your hacks, exams and other assignments using this site.

Some other School of Computing (Soc) and university computing resources and policies can be found at the following:

• SoC Website: http://computing.unl.edu

• UNL Computing Policy: http://www.unl.edu/ucomm/compuse/

• SoC Academic Integrity Policy: http://computing.unl.edu/academic-integrity-policy

• SoC System Frequently Asked Questions (FAQ): http://computing.unl.edu/faq

• SoC Undergraduate Advising Page: http://computing.unl.edu/advising

• SoC Student Resource Center: http://computing.unl.edu/src

Peer Programming Pair-Up

For students in online section(s): you may complete the lab on your own if you wish or you may team up with a partner of your choosing.

For students in the on campus section: your lab instructor may team you up with a partner.

To encourage collaboration and a team environment, labs are be structured in a peer programming setup. At the start of each lab, you will be randomly paired up with another student (conflicts such as absences will be dealt with by the lab instructor). One of you will be designated the driver and the other the navigator.

The navigator will be responsible for reading the instructions and telling the driver what to do next. The driver will be in charge of the keyboard and workstation. Both driver and navigator are responsible for suggesting fixes and solutions together. Neither the navigator nor the driver is "in charge." Beyond your immediate pairing, you are encouraged to help and interact and with other pairs in the lab.

Each week you should alternate: if you were a driver last week, be a navigator next, etc. Resolve any issues (you were both drivers last week) within your pair. Ask the lab instructor to resolve issues only when you cannot come to a consensus.

Because of the peer programming setup of labs, it is absolutely essential that you complete any pre-lab activities and familiarize yourself with the handouts prior to coming to lab. Failure to do so will negatively impact your ability to collaborate and work with others which may mean that you will not be able to complete the lab.

Lab Objectives & Topics

At the end of this lab you should be familiar with the following

• The Eclipse IDE that you'll use for this course (recommended)

• Cloning lab code from Github using Eclipse

• Modifying, compiling and executing your first Java program

• Using codepost.io to view grader feedback

Activities

Getting Started

Let's get started. In order to develop programs in Java you'll need:

• a code editor (plain text editor) to write your code
• a compiler to compile the Java code into Java Bytecode that can be run by a Java Virtual Machine (JVM), and
• a runtime environment to actually execute your program

To do this, we'll walk you through how to use Eclipse, a popular (and free) IDE (Integrated Development Environment).

1. You'll first need a Java Development Kit (JDK). You may already have "Java" installed but likely it is the Java Runtime Environment (JRE) that allows you to run Java programs. The Dev Kit allows you to develop (write) programs. We recommend installing Amazon's Corretto JDK: https://aws.amazon.com/corretto/

2. Got to Eclipse.org and download/install the Eclipse IDE. It is perfectly fine to use an alternative IDE if you wish, but instructions for all labs will assume Eclipse.

Creating a New Project

Using Eclipse

1. Once installed, start Eclipse
2. Choose a workspace directory/folder where you want all of your future projects to exist.
3. Close the Welcome screen, and create a new project:
   a. Select: File > New > Project
   b. Select Java Project when prompted by the New Project Wizard; click Next
   c. Enter a name for your project (Lab01)
   d. Be sure that the "Create module-info.java" is unchecked; click Finish
   e. Open the Lab01 folder in the Package Explorer View and find the src folder
   f. Right-click on the src folder and select New Class and name it Hello
   g. This should open a new source code editor. Make your program look like the following and save it.

public class Hello {

  public static void main(String args[]) {
    System.out.println("Hello World!");
  }

}

4. Run your program by clicking the "play" button in the tool bar

Congratulations on your first program!

Checking Out Code From Github

Each lab will have some starter code and other artifacts (data files, scripts, etc.) that will be provided for to you. However, the code is hosted on GitHub and you must check it out.

1. First we need a Git perspective (a context in the Eclipse User Interface that will allow us to work with Git). To open the Git perspective, click on the Open Perspective tab in the upper right:

   

2. Select Git from the menu and click OK

3. Click the Clone a Git repository in the Git Repositories navigation menu:

   

4. Copy/paste or type into the URI field, the URL: https://github.com/cbourke/CSCE155-Java-Lab01 and click Next

   

5. Once Eclipse has cloned the project, the master branch should be selected (checkbox); click Next again.

   

6. Select the directory where you want your project to be saved.
   Caution: the default option may not correspond to your default workspace. You may want to change it to your workspace, but the choice is yours. Also mark the Import all existing projects after clone finishes checkbox option or you will need to manually import the cloned project into Eclipse.

   

7. Switch back to your Java or JavaEE perspective and you can see your cloned project.

8. Run the Hello.java program in this project to verify everything works.

   Observe that this version of the program is in a different package. Java organizes code and classes using directories (folders) or "packages". This class has been placed into a directory/package named unl under yet another subdirectory/folder/package called soc.

Modify the Program

1. Modify the Hello.java program by changing the author to you (and your partner) and change the date.

2. Add a new line below the line that prints Hello World! that prints I love the School of Computing! using the other line as an example.

3. Rerun the program to verify it compiled and runs.

Submitting & Grading Your Program

Nearly all of your assignments (labs, hacks, exams) will include a programming portion that will require you to hand in source files for graders to compile and evaluate. To do this, we use a web-based assessment app called codepost.io (https://codepost.io).

You should have received an invitation to this website from your instructor through your email account (typically your @huskers.unl.edu email or whatever email you have associated with on Canvas). If you have access, great. If not, go to https://codepost.io/forgot-password and "reset" your password (even if you never initially set one). Be sure to use your huskers email or whatever primary email is associated with your canvas profile.

To hand in and grade your lab, do the following.

1. Login to https://codepost.io. It should immediately take you to the assignment submission page:

3. Click "Upload Assignment" which will bring up a dialog box:

Click "Upload files" and select the Hello.java source file from directory where your Eclipse project is located. Then click

4. You should see something like the following:

HOWEVER this does not mean that your program(s) worked, only that they were uploaded. You still need to view the results!!!

5. Click on to view the test results which will give you more details. If any test(s) failed, you should see:

You can click on the + button to see more details. However, if all tests passed, you should see something like this:

Some things to understand about the grading process:

• If there are problems or errors with your program(s), you should fix/debug them and repeat the handin/grading process. You can do this as many times as you like up until the due date.
• Some programs and assignments may require the output to be exact including any upper/lower case text and numbers accurate to a certain number of decimal points
• Some programs and assignments may only require part of the output to be correct and may ignore other formatting (spaces for example).
• Some programs and assignments may need to be manually examined by graders to award points.
• Some programs and assignments have more sophisticated test suites that run hundreds or thousands of tests.
• In any case, it is your responsibility to read, understand and address any and all errors and/or warnings that the grader produces.
• The grader is a black box tester meaning you don't have access to its internal workings. You should properly and thoroughly test and debug your programs locally instead of relying on it as a "blind tester."

Congratulations on your first lab!