The purpose of this assignment is to introduce you to programming in Java and familiarize you with the mechanics of preparing and submitting assignment solutions. Your goal this week is to learn to use DrJava for editing, compiling, and executing programs.

Hello, World.  The purpose of this step is to set up your computer for developing Java programs.

• Working at home. If you want to work on your home computer, follow the step-by-step instructions for your operating system: Windows, OS X, or Linux. If you are familiar with your operating system, you should be able to finish this part on your own. If you are hesitant, bring your laptop to Friend 017. The lab is staffed in the evenings with knowledgeable TAs who can assist you. Don't be afraid to ask for help.

• Working in a public cluster. If you prefer to work in one of the OIT public clusters follow the instructions for Windows or Mac OS X (depending on which you will be using), but skip the steps that involve installing software because Java and DrJava are already installed. Go straight to the "Create the program" instructions. Save your programs on your H: drive. If you are hesitant, work in Friend 017. The lab is staffed most evenings with knowledgeable TAs who can assist you. Don't be afraid to ask for help.

Programming.  Your job is to write two short programs on your own. We'll assume that you've already created, compiled, and executed HelloWorld.java by following the instructions in the previous part of the assignment.

1. Command-line arguments. Read Section 1.1 of the textbook. Modify UseArgument.java to make a program HiFour.java that takes four names as command-line arguments and prints out a proper sentence with the names in the reverse of the order given, so that, for example,

   % java HiFour Alice Bob Carol Dave
   

   outputs

   Hi Dave, Carol, Bob, and Alice. 
   

2. Integer variables. Read Section 1.2 (through page 22) of the textbook. Write a program SumThree.java that reads in three int command-line arguments, x, y, and z. The program then outputs all three integers and their sum in the form of an equation.

   % java SumThree 2 5 8
   2 + 5 + 8 = 15
   

Program style and format.  Now that your program is working, go back and look at the program itself. Did you include a header that will tell the reader who wrote the program, what it does and how to compile and run it? For full marks, your program should not only work correctly, but should conform to the recommended style and format so that it is easy to follow. Read Booksite Appendix B: Writing Clear Code. Follow the guidelines in the Formatting section of the Checklist.

Writeup.  With each assignment you must submit a text file named readme.txt that is a narrative description of your work. We provide a readme.txt that you should use as a template. Download this file and answer all questions in the space provided. You will need to read the COS 126 Collaboration Policy in order to answer the related questions in your readme file.

Questionnaire.  Part of this assignment is to fill out the following brief questionnaire.

Browsing the course website.  The next part of the assignment is to browse the COS 126 website. The address is:

http://www.princeton.edu/~cos126

Submitting the assignment.  The final part of the assignment is to submit HelloWorld.java, HiFour.java, SumThree.java, and readme.txt via the Web submission system called Dropbox. To do this, click the Assignments link from the course website; click the Submit link for that assignment; and (if you aren't already logged in) login using your OIT NetID and email password. Upload the required files, and click the Check All Submitted Files button. Your programs should compile without errors or warnings; if not, fix the problem and resubmit the appropriate files. Remember that every file you submit needs to have your name, netID, and precept number.

Getting help. If anything is unclear, don't hesitate to drop by office hours, post a question on Piazza or email us. We also recommend reading the checklist, which provides some clarifications and answers to frequently asked questions.