This quick tutorial will show you how to create a file, compile, and run it from the command-line.  We will use the "nano" editor in this tutorial.  You will need a Mac to do this tutorial.

1. Open the Terminal application on your Mac. When I open mine, I see:
    Last login: Mon Feb  6 14:54:25 on ttys002
    $
    
    (your "prompt" may look a little different--that's OK)
    
2. Let's "change directory" to your Desktop.  At the "$" prompt, type (don't type the $):
   $ cd ~/Desktop
    
3. Create a folder called "HowToCompile".  
   $ mkdir HowToCompile
   (you should see this folder appear on your Desktop)
   
4. Go into the "HowToCompile" folder:
   $ cd HowToCompile
   
4. Create two more folders inside "HowToCompile" called "src" and "bin".
   $ mkdir src
   $ mkdir bin
   
5. We're going to use the "nano" editor now to create a file inside the "HowToCompile/src" folder:
   $ nano -w src/HelloWorld.java
   
6. You are now running the "nano" program.  At the top of your screen, you should see:

GNU nano 2.0.6                File: src/HelloWorld.java                              

   and at the bottom of the screen, you should see:
   
                                            [ New File ]
   ^G Get Help    ^O WriteOut    ^R Read File   ^Y Prev Page   ^K Cut Text    ^C Cur Pos
   ^X Exit        ^J Justify     ^W Where Is    ^V Next Page   ^U UnCut Text  ^T To Spell

7. The "^" symbol stands for the "control key."  So if you press Ctrl-x, you will Exit the program.  Try it now.  Press Ctrl-x.

8. You should be back at the command-line prompt (the $).

9. Start nano again:
   $ nano -w src/HelloWorld.java
   
10. But this time, highlight the following source code, copy it using Command-C, and then paste it into nano using Command-V.

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

11. Now press Ctrl-x.  But notice that since you put text in the window, nano will ask you if you want to save.  You should see the following at the bottom of your screen:

Save modified buffer (ANSWERING "No" WILL DESTROY CHANGES) ?                                   
 Y Yes
 N No           ^C Cancel

12. Press the 'y' key.

13. nano will now ask you what you want to call the file:

File Name to Write: src/HelloWorld.java                                                        
^G Get Help            ^T To Files            M-M Mac Format         M-P Prepend
^C Cancel              M-D DOS Format         M-A Append             M-B Backup File

14. Press the "return" key to accept the name as-is ("src/HelloWorld.java").

15. You should be back at the command prompt ($) again.  Now, let's compile our Java file in src using javac and make sure that the compiled class file goes into bin:

   $ javac -d bin src/*.java
   
16. Notice now if we "list" the contents of the bin directory, we should see our HelloWorld.class file:

   $ ls -al bin
   total 8
   drwxr-xr-x  3 dbarowy  staff  102 Feb  6 15:09 .
   drwxr-xr-x  5 dbarowy  staff  170 Feb  6 15:00 ..
   -rw-r--r--  1 dbarowy  staff  426 Feb  6 15:09 HelloWorld.class
   
17. Let's run the program now.

   $ java -cp bin HelloWorld
   Hello world!