1. Confirm lab access
2. Confirm your ability to log into the lab computers
3. Set up your account
4. Create a Java program in Visual Studio Code (VSC)
5. Compile and run the program from the command line
6. Compile and run the program from within VSC

Lab Access

Logging In

Terminals

Directory setup and some Unix

    xena@loin ~$> pwd
    /home/xena

Now make a new subdirectory for all of your work in this course. Call this directory "CS113". (I usually use capital letters to start directory names. This is not required, it is just convenient.) To do so, use the Unix mkdir command as shown

    xena@loin ~$> mkdir CS113

    xena@loin:~$ ls
CS113	 Documents  local  mpub		 Music	Pictures  public_html  tmp
Desktop  Downloads  mail   mpublic_html  Node	Public	  Templates    Videos

Now go into the CS113 directory and make a new directory there to hold things you will do today. Then switch into the directory you just made

        xena@loin:~$ cd CS113
        xena@loin:~/CS113$ mkdir Lab01
        xena@loin:~/CS113$ cd Lab01
        xena@loin:~/CS113/Lab01$ ls
        xena@loin:~/CS113/Lab01$ pwd
        /home/xena/CS113/Lab01
        xena@loin:~/CS113$ cd
        xena@loin:~/CS113/Lab01$ pwd
        /home/xena/
        xena@loin:~/CS113$ cd CS113/Lab01
        xena@loin:~/CS113/Lab01$ pwd
        /home/xena/CS113/Lab01
    

For each homework and lab, you should do something like the above to create a new clean place for the work you are about to do. That is, create a HW01 directory, a LAB02 directory, etc.

Now lets do something using Visual Studio Code (VSC).

Leave the terminal open, we will return to it

A Program in VSC

Start VSC. You can do this either from the terminal by entering code or from the dots gird in the lower left (as you did for starting a terminal).

Within VSC, select File Menu / "Open Folder"; then navigate to the Lab01 directory you just created and open that folder. Hint, always select the exact folder you want, not one of its parents.

On the left, click on the extensions button (3 squares together and one slightly apart (usually at the bottom)) and confirm in the list of installed extensions that "Extension Pack for Java" is installed.

On the left, click of the top icon -- a document on top of a document.

Put the mouse over "CS113". Just to the right you should get a set of icons. Click on the leftmost -- a document with a plus in the lower left.

Just below a box should appear with a blinking cursor waiting for you to type. Enter "HelloWorld.java" then hit return

Now on the right, start entering the hello world program given below

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

Compile and run

xena@loin:~/CS113/Lab01$ ls
HelloWorld.java
xena@loin:~/CS113/Lab01$ javac HelloWorld.java
xena@loin:~/CS113/Lab01$ ls
HelloWorld.class  HelloWorld.java
xena@loin:~/CS113/Lab01$ java HelloWorld
Hello World

Back in VSC

1. Open a terminal inside VSC and do the javac/java thing there. To open a terminal in VSC, select "Menu Terminal / New Terminal". This terminal has the same behavior as the terminal you opened earlier.
2. Just above the "main" function are the words "Run" and "Debug" (for me they are light grey). Click on "run" or "debug". This can fail sometimes when the compile and run in the terminal works.
3. Up near the top of the VSC window there is an arrow pointing right. Click on it to compile and run your program. This can fail sometimes when the compile and run in the terminal works.

Once your Hello World program works, modify it to print "hello world" at least 5 times.

Unix Recap

Unix -- Part 2

Recall that in the last lab you used the following Unix commands

Copy

    UNIX$ cp Lab01/HelloWorld.java Lab02/HelloWord2.java

Now change your directory to Lab02 and compile the file. If everything went correctly, you should have gotten the following error message

    HelloWorld2.java:1: error: class HelloWorld is public, should be declared in a file named HelloWorld.java
            public class HelloWorld {
                   ^
    1 error

    cp HelloWorld2.java HelloWorld.java

Unix rm and mv

1. delete the file HelloWorld2.java
2. Do copy in the first place, move (rename) it.

rm HelloWorld.java

Usually the better option than copy followed by remove is to simply rename the file. For instance

    mv HelloWord2.java HelloWorld.java

scp

"scp" acts much like "cp" EXCEPT it can copy files from your labtop to Unix, or the converse.

To use scp open a terminal window on your laptop. Use cd to navigate to a directory with the file you want to upload to Unix. Then scp it to a directoy on the Unix system. For instance, suppose on Unix you have a directory named Lab02 in a CS113 directory which is in your home directory. On your laptop you have the same directory structure. Further suppose that on your laptop you have a file named Readme that you want to get to Unix. Given this setup, so the following:

    // open a terminal on your laptop
    $ cd
    $ cd CS113/Lab02 //
    $ ls
    // A listing of files one of the files is Readme
    $ scp Readme UNIX_NAME@goldengate.cs.brynmawr.edu:CS113/Labo2/Readme 

    Readme                                                  100%  162     5.6KB/s   00:00

Java

Leap Year

public class LeapYear {
   public static void main(String[] args) {
       int year = Integer.parseInt(args[0]);
   }
}

java LeapYear 2020
true
 
java LeapYear 2021
false
 
java LeapYear 1600
true
 
java LeapYear 1900
false

Valid Triangle

public class ValidTriangle {
   public static void main(String[] args) {
       int s1 = Integer.parseInt(args[0]);
       int s2 = Integer.parseInt(args[1]);
       int s3 = Integer.parseInt(args[2]);
   }  
}

Here are some cases

java ValidTriangle 7 10 8
true
 
java ValidTriangle 40 12 15
false

What to hand in