ce02 Command Line Compilation and Packages

This exercise is designed to introduce text editors as well as how to compile Java code organized into packages on a Unix system.

Prerequisite Knowledge

Course-Specific Learning Outcomes

LO1.a: Navigate and modify files, directories, and permissions in a multi-user Unix-like environment.
LO1.c: Create and modify text files and source code using a powerful terminal-based text editor such as Emacs or Vi.
LO1.d: (Partial) Use shell commands to compile new and existing software solutions that are organized into multi-level packages and have external dependencies.

Questions

In your notes, clearly answer the following questions. These instructions assume that you are logged into the Odin server.

NOTE: For each step, please provide in your notes the full command that you typed to make the related action happen along with an explanation of why that command worked. Some commands require multiple options. It is important to not only recall what you typed but also why you typed each of them. If done properly, your class notes will serve as a helpful study guide for the exam.

Exercise Steps

Checkpoint 1 Steps

In your home directory on Odin create the subdirectory structure seen below. What single command can be used to create all of these directories at once?
```
exercise2
 |--- src
       |--- cs1302
             |--- example
```
Navigate to the src directory. In this example, src is the default package directory for source code. Inside of the src directory, create a file called Hello.java. Within this file, write a Java program to prompt the user for their name, read in their full name and then output Hello, <user> with their name instead of <user>. Your program should work without any import statements. Sure, this is possible! In your notes, write the full line of java code to instantiate a Scanner object without importing the class.
Compile and run your code directly from the default package. Don't use the -d option for javac in this step. In which directory is the compiled code contained?

Once you are confident that it is working, remove the compiled (byte) code (not your source code).
Move the Hello.java file (source code) into the cs1302.example package. What two things must be done to accomplish this? Hint: Named Packages
For better organization, let's separate the source code from the compiled code. Directly inside the exercise2 directory, add a subdirectory called bin. This directory will be the default package for our compiled code. From within exercise2, what is the single command to compile Hello.java and place the compiled code into the bin directory? Remember to use tab completion when typing in Unix to avoid mistakes and save you time!
From the exercise2 directory, what is the single command to run the Hello program?
From your home directory (not exercise2), what is the single command to run the Hello program?
Execute the find command from directly within your exercise2 directory. If the previous steps were executed correctly, you should see the following output:
```
.
./src
./src/cs1302
./src/cs1302/example
./src/cs1302/example/Hello.java
./bin
./bin/cs1302
./bin/cs1302/example
./bin/cs1302/example/Hello.class
```

Checkpoint 2 Steps

Navigate to the exercise2 folder and add a cs1302.utility package directory to your heirarchy. Add a class called MyMethods to this package. Add a single, static method to to this class which takes two int variables as parameters and returns the maximum of the two as an int. What is the exact first line of code in MyMethods.java?

PROTIP Unless it is specifically stated, it is best to always work from the main exercise directory. For example, while working on the source code for this exercise, you can modify all of the files without leaving the exercise2 directory by providing the relative path (using tab completion) to the file from the exercise2 directory. This means you would rarely use the cd command while working on an exercise. When Unix beginners overuse the cd command, they often find themselves lost in the directory structure which can lead to mistakes and, in rare cases, frustration!
Assuming your present working directory is still exercise2, what is the command to compile MyMethods.java and place the byte code in the bin directory? Remember, there are no dependencies when compiling MyMethods.java as it does not depend on any other source code.

Look in the bin directory now that you've compiled both Hello.java and MyMethods.java. Notice the directory hierarchy that was automatically created.
Now, modify your Hello class. Have it print out the maximum of two values input by the user. Use the method from your MyMethods utility class. What is the line of code to call this method, assuming you have no import statements in Hello.java?
TRICKY What is the command to compile the Hello class from the exercise2 directory and place the compiled code into bin? Note: there is now a dependency in Hello.java. It relies on the code from MyMethods, so the compiler needs to know where to find that class. Hint: Setting the Class Path
Now, add the import statement for MyMethods in Hello.java and replace applicable fully qualified names with simple names. Rerun your code to make sure it is working. From the exercise2 directory, what is the single command to run the Hello program?

Execute the find command from directly within your exercise2 directory. If the previous steps were executed correctly, you should see the following output:

.
./src
./src/cs1302
./src/cs1302/example
./src/cs1302/example/Hello.java
./src/cs1302/utility
./src/cs1302/utility/MyMethods.java
./bin
./bin/cs1302
./bin/cs1302/example
./bin/cs1302/example/Hello.class
./bin/cs1302/utility
./bin/cs1302/utility/MyMethods.class

Submission Steps

Each student needs to individually submit their own work.

Create a plain text file called SUBMISSION.md directly inside the exercise2 directory with the following information:
1. Your name and UGA ID number;
2. Collaborator names, if any; and
Here is an example of the contents of SUBMISSION.md.
```
1. Sally Smith (811-000-999)
2. Collaborators: Joe Allen, Stacie Mack
```
Change directories to the parent of exercise2 (e.g., cd .. from exercise2). We will use the tar command to combine our directory hierarchy into a single file for backup purposes. To do this, execute the command:
```
$ tar -cf exercise2.tar exercise2/
```
Read the manual page for tar in section 1 of the manual to learn more about tar and its various options.
List the contents of your directory and make sure you see exercise2.tar. Now, to make sure this tar file contains all of the work you just did, list all of its contents with the command:
```
$ tar -tf exercise2.tar
```
Now, to make this file smaller, we will compress it with gzip. Execute the command:
```
$ gzip exercise2.tar
```
Read the manual page for gzip in section 1 of the manual to learn more about gzip and its various options.
List the contents of your directory and make sure you see exercise2.tar.gz instead of exercise2.tar. Now, you have a compressed backup of your directory saved in the .tar.gz file.
Use the submit command to submit this exercise to csci-1302:
```
$ submit exercise2 csci-1302
```
Read the output of the submit command very carefully. If there is an error while submitting, then it will displayed in that output. Additionally, if successful, the submit command creates a new receipt file in the directory you submitted. The receipt file begins with rec and contains a detailed list of all files that were successfully submitted. Look through the contents of the rec file and always remember to keep that file in case there is an issue with your submission.

Note: You must be on Odin to submit.

Copyright © Michael E. Cotterell, Bradley J. Barnes, and the University of Georgia. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License to students and the public and licensed under a Creative Commons Attribution-NonCommercial 4.0 International License to instructors at institutions of higher education. The content and opinions expressed on this Web page do not necessarily reflect the views of nor are they endorsed by the University of Georgia or the University System of Georgia.

cs1302uga / cs1302-ce02