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Assignment 0: Developing Java Programs

Objectives:

Due: Friday before class

Part 0: Set Up

Cloning the Repository

In your terminal, go to the directory where you are keeping your repositories for CSCI209. Clone the repository for this assignment.

Optional: Check out GitHub's Student Developer Pack and sign up if you're interested.

README

In a text editor, open up the README file. Add your name to the README, specifying that you're the author/owner of the repository.

Part 1: Your First Program

In your favorite text editor, create a Java class called Intro in a file named Intro.java. The Intro class's main method should print out--on separate lines--your name, your favorite color, and your favorite pop culture character. For example: 

Sara Sprenkle
Favorite Color: Purple
Favorite Pop Culture Character: Tina Belcher

All the top-down design principles from CS111 and CS112 apply in every computer science course. Do not try to write the entire program in one attempt. Break the problem into manageable pieces. Branch/commit/merge at good checkpoints.

You should write only a little code at a time, then compile and execute it (see directions below) so that you find bugs quickly. Since yu're getting used to the new Java syntax, you'll likely run into problems. When that happens, compare your code to the examples from class.

Make sure your program is well-documented and has the appropriate format, as discussed in class.

Compiling the Program

In a terminal, from the directory that contains Intro.java, compile your program using javac Intro.java

If there are errors, fix those errors and re-compile until it compiles.

Executing the Program

In a terminal, from the directory that contains Intro.java, execute your program using the command
java Intro

If the output is not what you expect, edit your program, recompile, and execute. Remembering to recompile before executing will be hard to get used to at first. Keep in mind some of the benefits of compiling: it catches syntax errors and can improve the efficiency of your executing program. Once compiled, you can run your program multiple times (which, granted, is not too interesting at this point.)

When you're sure your program is working correctly, execute your program using the command
java Intro > output, which writes the output from java Intro into the file output.

Note that the file name has no extension, and that's fine. It's just a text file.

Add your source code and output to the repository.

If you are spending more than about 30 minutes on this program, something is wrong. Talk to me.

Part 2: Debugging A Program

Objective: The goal of this part of the assignment is to get you familiar with the required Java syntax, the compiler's error messages, and how to fix the errors so that the program compiles. Debugging is one of the most important skills you learn from programming, so it's good to practice, especially on a small program that you did not write. (Debugging your own code can be emotional; let's take that emotion out -- you're finding someone else's bugs!)

The given Assign0.java program contains at least 4 errors. Some are compiler errors that the compiler will catch. Others are logic errors that the compiler won't catch. The errors are common--you'll likely make these mistakes yourself at some point in time. You'll find those bugs faster in the future since you've practiced debugging them.

Comment out the original code and note the cause of the error (e.g., the rule that is violated). Then, correct the code. It is not enough to say how you changed the code; you must explain the cause of the error. You prove to me that you know how to fix it by what you put in the code. The comments prove that you understand why the error occurred.

Aim for the fewest number of changes to get the code to work as expected. You could rewrite the code from scratch, but that's not the goal/point of the assignment.

Since you are inexperienced with Java, what are good ways to figure out the errors? You should have several different approaches to solving these problems (and that doesn't involve Web searches).

Rationale for requiring comments: I could do a diff between the original version of the code and your version of the code to see what you changed. But, I want you to show that you know why the error occured.

Example buggy line of code: System.out.println("")
(i.e., the error is that there is no ; to end the statement).

Tell me why this is a problem, e.g., "Java statements end in ;. This statement is incomplete/doesn't end until there is a ;." There are a variety of other ways you can tell me the cause. Focus on the problem, not the solution (I can see if you implemented the solution).

What not to write:

Hopefully, these kinds of exercises help you realize why you should not write a lot of code before compiling.

Saving the Final Output

After you're sure the program works correctly, save the output in a file called debugged.out, similar to how you did in the last problem. Add the output file to your repository. Make sure your working version of the code is in the repository.

Cleaning up your code

Great! You got it working! Before your final submission, review your code. Is your code written in an (relatively) understandable way? Any extra code that you no longer need? Do you have appropriate comments? Does the code's indentation look like the examples?

Submission

Submit your assignment by pushing the code, README.md, and output files to GitHub. Note that the .class files should not be included in the repository. I set up the .gitignore file to prevent you from adding the .class file.

Checking your work

It is recommended that you confirm in the GitHub web interface that your final submission is in the repository. You can [re?]clone your project in a new directory, and then make sure that you can compile and run your programs. (This is, afterall, the process that I'll use to grade.)

Grading (70 pts)

You will be evaluated based on