Computer Science 523
Advanced Programming

Summer 2014, The College of Saint Rose

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This first "mini" lab is designed to help you get set up with BlueJ, a simple integrated development environment (IDE). After this lab, you will not be required to use BlueJ, but I want everyone to be familiar with it, as I will be using it for my own in-class development, and class examples and lab sample solutions will be distributed as BlueJ projects.

You are to work alone on this lab, but please feel free to ask for as much help as you need from your instructor and/or classmates.

Introduction and Setup

There are two major types of programs we will be developing this semester: Java applets and Java applications. More soon on the differences between them and when we'll use each, but for now we will work through an exercise to run one of each in BlueJ.

It is important to keep up - ask if you are having trouble at any step. For today, everyone should use one of the lab computers. If you would like to use your own computer later, we will see soon how to set that up. It's all free software, available for any computer that can run Java.

• Create a folder where you will store your work for this course. It is essential that you choose a location that is on your network storage space (the "H" drive) so it will be available on any computer in the lab (and in fact, on computers in labs all over campus). I suggest calling your folder something like "CS523" without any spaces.
• Launch BlueJ by clicking its icon on the desktop. A mostly blank window, called the project window, with some greyed out buttons, should appear.
• From the "Project" menu, choose "New Project". In the window that pops up, navigate to the folder you created above, then enter "Lab0", again with no spaces in the "File" box, then click "Create". You should now see an icon in your BlueJ window that looks like a sheet of lined paper, and the buttons on the left side should now be active.

Important note: be sure to get into the habit of naming your folders and files for this course without any spaces. Spaces in the names can cause a variety of problems later.

Running a Java Application

First, we'll run a Java application in BlueJ. These are programs that interact with you through the keyboard and screen (the "terminal").

• Go to the project window and click the "New Class" icon. In the "Class Name" field, this time enter "HelloWorldApplication" (still no spaces, of course) and select the "Class Type" as "Application Class", then click "Ok". Another icon should appear in your project window labeled "HelloWorldApplication".
• Double-click the new "HelloWorldApplication" icon. This should bring up an editor window with the skeleton of a program that we will use as a starting point. You should see text displayed in a few colors and some of it within shaded boxes. We will learn all about what's going on there as we go forward.
• Click the "Compile" button at the top of the editor window. If all goes well, you should see a message at the bottom of the editor window: "Class compiled - no syntax errors".
• Return again to the project window. The "HelloWorldApplication" icon should no longer have the diagonal lines across it. And now we're ready to run the program. Right-click on the "HelloWorldApplication" icon, which should bring up a menu. Choose the entry "void main(String[] args)". A window will pop up. For now, we don't need to do anything with this window beyond hitting "Ok". If all goes, well, your program will run and you'll get back to the project window. Since the program doesn't ask Java to do anything, this behavior is exactly right, though incredibly boring.
• Now, we'll make this program slightly more interesting. Switch back to the "HelloWorldApplication" window. You'll see the skeleton of Java application. Add to the main method a simple printout:

     System.out.println("Hello, Java application world");
  

• Run the program again (that is, compile it, then choose the "void main(String[] args)" menu item when you right-click on the class icon in the project window). This time, a new window should pop up with your program's output. This is the "terminal" window, through which we will interact with our Java application programs.
• Now, go back to the editor window and change the paragraph at the top to a message that briefly describes what you just did (a sentence or two is sufficient here), and replace the "(your name)" after the @author with your name. There is no need to leave the parentheses. Re-compile (the "Compile" button) and re-run to make sure it still works.
• Finally, to make sure your program looks pretty, go back to the editor window and choose "Auto-layout" from the "Edit" menu. This will indent all of your code nicely (more on this later). Re-compile and re-run one last time to make sure everything still works.

Running a Java Applet

Next, we will see how to run a Java Applet in BlueJ. Applets are programs that interact with their users through one or more graphical user interface screens (buttons, menus, text fields, etc.). These types of programs can be run in a standalone mode, but are often run by embedding them in web pages.

• Go back to the project window and click the "New Class..." button. In the "Class Name" field, enter "HelloWorldApplet" (remember: no spaces) and make sure that the "Class Type" is selected as "Standard Class", then click "Ok". You should now see another icon in your project window labeled "HelloWorldApplet" and with some diagonal lines across it.
• Double-click on the new "HelloWorldApplet" icon. Again you will be brought into the BlueJ editor, but the starting text this time will look a little different.
• Click the "Compile" button at the top of the editor window. If all goes well, you should see a message at the bottom of the editor window: "Class compiled - no syntax errors". We really can't run this program yet.
• We need to add a few items to the program to turn it into a Java applet. First, we need to add some import statements to the top of the program. Normally, we will list the specific classes we wish to import, but for now, we will import a large collection of them. At the top of your program (anywhere before the class header "public class HelloWorldApplet"), add

  import java.awt.*;
  import javax.swing.*;
  

  And then in the class header, add "extends JApplet", making your class header

  public class HelloWorldApplet extends JApplet
  

• Click "Compile" again and to make sure you didn't introduce any errors.
• Now, go back to the project window. The "HelloWorldApplet" icon should no longer have the diagonal lines across it. And now we're ready to run the program. Right-click on the "HelloWorldApplet" icon, which should bring up a menu. The first item in that menu is what you want: "Run Applet". Choose this. A window should pop up. Make sure "Run Applet in appletviewer" is selected at the top, and hit "Ok". A brand new window should appear, mostly if not completely blank and white. Congratulations, you have run a Java applet, albeit an incredibly boring and useless one. Close this window when you are done admiring it.
• To make our program slightly more interesting, we are going to make it display a message in this window. Go back to the editor window, the one with the program text. Inside the class (between the { and }, type the following method definition, exactly as you see it here, including all spacing and punctuation:

       public void init() {
          
          add(new JLabel("Hello, Java Applet world!"));
      }
  

• Now hit the "Compile" button again on the editor window, and choose "Run Applet" again from the popup menu on the "HelloWorldApplet" icon on the project window. The window that comes up should now have a message displayed.
• Like you did with the applet program, put your name into the "HelloWorldApplet" program, reindent your program with the "Auto-layout" entry under "Edit", and re-run to make sure things still work. (the "Run Controller" menu item) the program to make sure you didn't break anything.

Creating and Submitting an Archive File

Your last task is to create a single archive file that you can submit through our SubmissionBox system. In Windows, you can do this by choosing the "7z" option or the option to create a "Zip Archive" when you right click on a folder. Navigate to your "H:" drive in the Windows Explorer, and go into your "CS523" folder. Create a Zip archive of your "Lab0" folder that contains the Java programs you just wrote.

To submit, Upload a copy of your lab (the .7z or .zip file you just created that contains your project directory) using Submission Box under assignment "Lab0".

Grading

This assignment is worth 10 points, which are distributed as follows: