CS 206 - Introduction to Data Structures

Lab 1

Unix and Visual Studio Code

Friday, Sep 11

Part 0: Access

Part 1: UNIX

Before you can being using UNIX, you need to get onto a unix computer. If you are working with your own machine do the following:

MAC

1. Open a terminal. (The app is in applications/utils)
2. Use the ssh command to open a session to CS a CS machine. The command is ssh YOUR_CS_NAME@powerpuff.cs.brynmawr.edu. You will be asked for your CS department password. Enter it.
3. That is it. You are now at a UNIX prompt on the CS department machine named powerpuff.

Windows 10 PC

1. Open a power shell. In the search barch in the lower left type "powershell"
2. Use the ssh command to open a session to CS a CS machine. The command is ssh YOUR_CS_NAME@powerpuff.cs.brynmawr.edu. You will be asked for your CS department password. Enter it.
3. That is it. You are now at a UNIX prompt on the CS department machine named powerpuff.

• cd
  Change directory
  Example: cd cs206 (change to the directory cs206) (Note that this will probably not work as you do not have a cs206 directory.)
  Example: cd .. (change to the directory one above where you are, for instance is you are in /home/xena/cs206, then cd .. would put you in /home/xena
  Example: cd with no argument. This returns you to your home directory
• ls
  Display all the files in the directory. It is very common to use the ls command immediately after cd.
  Example: ls cs206 list the files in the directory cs206 (if it exists)
  Example: ls list the files in the current directory
• mkdir
  Create a directory
  Example: mkdir cs206 make a directory named cs206 Actually do this in your home directory. To be sure you are in you home directory enter the command cd
• pwd
  Displays the current working directory

  cd ~
  mkdir cs206

Using Visual Studio Code to write Java programs

1. Start VSC
   1. Applications Menu / Programming / Code - OSS
   2. or Applications Menu / System Tools / Mate Terminal then in the terminal window enter the command "code &"
2. Check to confirm that the correct extension packs are installed
   1. Java Extension Pack
   2. PrintCode
   To check, tap on the 'square with the top right quadrant slightly moved' icon on the far left of the screen). Look through the 'enabled' list (just to the right of the icon) for both of these. If they are not installed tap in the search bar (above the enable list) and enter the name. Tap and follow on screen directions to install.
3. In the window that appears (it should say "Welcome") tap on "Open folder" under "Start".
   1. Navigate to the cs206 directory you just made above.
   2. In the upper right tap on the folder icon
   3. In the small popup, enter "Lab1"
   4. Tap on "create"
   5. Tap on "Add"
   6. Make sure the folder ou just created is highlighted then Tap on "open".
4. You can also create the lab1 folder using Unix as above. In that case you would just navigate to the lab1 folder and click on "open".
5. The left column should now say "Explorer" at the top. Just below that should be an entry for Lab1.
6. Create a new file "HelloWorld.java"
   1. Tap on the document with a '+' icon to the right of "Lab1". When you hover over this icon it should say "New File".
   2. type "HelloWorld.java"
7. Tap in the HelloWorld.java tab that should have just appeared.
8. Write a complete java implementation of a "hello world" program.
9. Run your program (to run do the following).
   1. Tap on the insect on the left edge of the screen
   2. Tap on "Run with Java" (Alternately tap on "run" that should have appeared just above you main method.)

More Java

1. Modify your hello world program to print out "hello World" and the count (ie "Hello World 1", "Hello World 2") a lot for times. (At least 610). Do not do this using 610 print statements.
2. Run your program

Write a program to count the number of lines in a file.

1. Start a new Program in VSC
   1. Return to the document view by clicking on the overlapping rectangles (upper left)
   2. Tap on the 'new file' icon to the right of "Lab1" Name the file "EchoCount.java"
2. Tap in the EchoCount.java tab (you should already be on that tab).
3. Enter the following program:

   	public class EchoCount
   	{
   	    public static void main(String[] args) {
   	        new EchoCount().echo();
   	    }
   
   	    public EchoCount()
   	    {
   	    }
   
   	    public void echo()
   	    {
   	        try (BufferedReader br = new BufferedReader(new FileReader("/home/gtowell/Public/206/lab01/descent.txt"));) {
   	            int lineCount=0;
   	            while (true) {
   	                String l=br.readLine();
   	                lineCount++;
   	            }
   	            System.out.println("Lines read " + lineCount);
   	        } catch (FileNotFoundException fnf) {
   	            System.err.println("Could not open the file" + fnf);
   			} catch (IOException ioe)
   	        {
   	            System.err.println("Reading problem" + ioe);
   	        }
   	    }
   	}	
   

4. After entering all of this, you should see many items with a squiggly red underscore; BufferedReader, FileReader, etc. The underscores indicate problems in your code. At each
   1. Position the cursor over the underscored text.
   2. A popup will appear, on the bottom line of the popup, tap on "Quick fix".
   3. Generally, this will suggest ways of fixing the problem. In these cases, the fix "Import". So select "import"
   4. The squiggly line should go away.
   (Red squggles indicate problems that you must fix for the program to run. Yellow squiggle indicate this it would be better to fix; you program will likely run fine but fixing is good practice.)
5. Run your program.
   1. Tap on the insect on the left edge of the screen
   2. Tap on "Run with Java"
6. Extend this program so that it prints the file being read in addition to printing the number of lines in the file.
7. Be sure you understand this program, you will the file reading method illustrated here for the rest of the semester.

Write a program to get input from the user.

      public void doUI() {
        int total=0;
        Scanner ss = new Scanner(System.in);
        while (total < 100) {
            System.out.print("Enter an integer (or Exit to quit)");
            String ll = ss.nextLine();
            if ("Exit".equals(ll))
                break;
            try {
                int ii = Integer.parseInt(ll);
                total += ii;
            } catch (NumberFormatException ee) {
                System.err.println(ll + " is not an integer");
            }
        }
    }

Once you program works, extend it so that the user is asked for input at most 10 times.

Write a program to calculate the Fibonacci sequence.

1. Create a new Class in VSC
2. (If needed) Return to the document view by clicking on the overlapping rectangles (upper left)
3. Right click on "Lab1" and select "New File". Name the file "Fibonacci.java"
4. Tap on the Fibonacci.java tab (you should already be there)
5. Write a java program to compute the Fibonacci sequence and the golden mean (the golden mean is the ration between two consecutive fibonacci numbers i.e., nI/n(I-1)). Your program should be able to calculate the fibonacci sequence to an arbitrary length. For now, 20 will do. Your program should generate a table like:

   		1 1 1.0
   		1 2 2.0
   		2 3 1.5
   		3 5 1.6666666666666667
   		5 8 1.6
   		8 13 1.625
   		13 21 1.6153846153846154
   		21 34 1.619047619047619
   		34 55 1.6176470588235294
   		55 89 1.6181818181818182
   		89 144 1.6179775280898876
   		144 233 1.6180555555555556
   		233 377 1.6180257510729614
   		377 610 1.6180371352785146
   		610 987 1.618032786885246
   		987 1597 1.618034447821682
   		1597 2584 1.6180338134001253
   		2584 4181 1.618034055727554
   		4181 6765 1.6180339631667064
   		6765 10946 1.6180339985218033
   	

   Here is the the core code for computing the fibonacci sequence. You will need to write a more code to make this useful.

   		int n_2=1;
   		int n_1=1;
   		for (int i=1; i<20; i++) {
   			int nI = n_2 + n_1;
   			n_1 = n_2;
   			n_2 = nI;
   		}
   	

   When calculating the golden mean (1.618....) you will want to watch out for an issue with integer versus floating point division
6. Run your program.
   1. Tap on the insect on the left edge of the screen
   2. Tap on "Run with Java"

What to Hand In

Send email to gtowell206@cs.brynmawr.edu with the following:

1. A completed table for the questions in the UNIX section
2. A copy of the last program you completed from the three above. It would be great if you did them all, but you may run out of time.