Computer Science 252
Problem Solving with Java

Fall 2014, The College of Saint Rose

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Agenda

• Welcome to Computer Science 252!
• Syllabus and administrative details
• SubmissionBox setup

  We will be using a system called "SubmissionBox," developed by software engineering students here at Saint Rose, for the submission of most of your work this semester. We'll start by making sure everyone can log in and submit a test assignment before we move on to the first in-class exercise.

  First, everyone will need to come up to get their SubmissionBox account set up (or updated, if you were in my CSC 202) to be used for this course.

  Once your SubmissionBox account is ready to go, create a document (a plain text or Word document, for example) and save it somewhere on your computer. Then log into SubmissionBox, and submit this document under assignment "SBTest". Verify that you received an email confirmation for this submission.

• In-class Exercise 1 - (15 lecture assignment points) due before the end of class.

  Before we get in to class examples, we will make sure everyone can run Java programs in the BlueJ development environment that we will be using all semester. 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 together 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.

  Here is the outline of our procedure:

  1. 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 "CS252" without any spaces.
  2. Launch BlueJ by clicking its icon on the desktop. A mostly blank window, called the project window, with some greyed out buttons, should appear.
  3. From the "Project" menu, choose "New Project". In the window that pops up, navigate to the folder you created above, then enter "InClass1", 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.

  4. Click the "New Class..." button. In the "Class Name" field, enter "HelloWorldWC" (remember: no spaces) and make sure that the "Class Type" is selected as "WindowController Class", then click "Ok". You should now see another icon in your project window labeled "HelloWorldWC" and with some diagonal lines across it.
  5. Double-click on the new "HelloWorldWC" 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.
  6. 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".
  7. Now, go back to the project window. The "HelloWorldWC" icon should no longer have the diagonal lines across it. And now we're ready to run the program. Right-click on the "HelloWorldWC" icon, which should bring up a menu. The last item in that menu is what you want: "Run Controller". Choose this. Two things should happen: a new red icon should appear at the bottom of the project window, and a brand new window should appear, mostly if not completely blank and white. This new window is one we will refer to as the "canvas". Congratulations, you have run a Java applet, albeit an incredibly boring and useless one. Close the canvas window when you are done admiring it.
  8. To make our program slightly more interesting, we are going to make it display a message on the canvas. Go back to the editor window, the one with the program text. On the blank line between the { and }, type the following line, exactly as you see it here, including all spacing and punctuation:

         new Text("Hello, objectdraw world!", 100, 100, canvas);
     

  9. Now hit the "Compile" button again on the editor window, and choose "Run Controller" again from the popup menu on the "HelloWorldWC" icon on the project window. The canvas that comes up should now have a message displayed.
  10. 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. Re-compile (the "Compile" button) and re-run (the "Run Controller" menu item) the program to make sure you didn't break anything.
  11. 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.
  12. Now, we'll run a Java application in BlueJ. Go back to the project window and click the "New Class" icon. In the "Class Name" field, this time enter "HelloWorldApp" (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 "HelloWorldApp".
  13. Double-click the new "HelloWorldApp" icon. Again you will be brought into the BlueJ editor, but the starting text this time will look a little different.
  14. 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".
  15. Return again to the project window. The "HelloWorldApp" icon should no longer have the diagonal lines across it. And now we're ready to run the program. Right-click on the "HelloWorldApp" icon, which should bring up a menu. The menu is different this time, and you should 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.
  16. Now, we'll make this program slightly more interesting. Switch back to the "HelloWorldApp" window. If you look more closely, you'll see a familiar-looking skeleton of Java application. Add to the main method a simple printout:

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

  17. 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.
  18. Like you did with the applet program, put your name into the "HelloWorldApp" program, reindent your program with the "Auto-layout" entry under "Edit", and re-run to make sure things still work.
  19. 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 "CS252" folder. Create a Zip archive of your "InClass1" folder that contains the Java programs you just wrote.

  Please submit only the file InClass1.zip in Submission Box under "InClass1" before you leave class.

• Event-driven programs

Lecture 1 Assignment

Due at the start of class, Thursday, August 28.

Please submit answers to these questions in Submission Box under "LA1" or in hard copy by the start of our next class. We will discuss these questions at the start of class, so no late submissions are accepted. Please be sure that your name is clearly indicated in all submissions.

Most of these are review of some of the Java concepts and constructs you should be familiar with from your previous programming experience.

1. I would like to get a better sense of everyone's backgrounds coming in. Please answer each of the following. (4 points)
   • What is your name, year, and major?
   • If you are not already one, are you considering a major or a minor in CS or IT?
   • Have you taken any other computer science, either before or at Saint Rose?
   • Do you have any programming experience other than the courses listed in the previous question? If so, which programming languages have you used and how complex were the programs you developed?
   • What was your high school and home town?
   • What is your favorite restaurant in your home town and what should I order there?
   • What types of computers (e.g., PC running Windows, Mac, Linux, tablets) have you used?
   • If you plan to use computers other than those in Saint Rose labs for course work, what type of computer do you plan to use?
2. In an effort to get to know you and to make sure you know how to find me, please stop by my office (Albertus Hall 400-2) and introduce yourself as a Computer Science 252 student (some time this week). (3 points)
3. Consider the following names that a programmer is considering for use as variable names in a Java program. For each one, indicate whether it is a valid Java identifier. If it is valid, does it conform to the Java naming convention for variables? For all names that are either invalid or do not conform to the naming convention, suggest a similar name that would be appropriate to use instead. (5 points)

   KNIGHT
   252assignments
   FavoriteColor
   darth vader
   BugsBunny!
   WHEN_IS_LUNCH?
   gotCash$$
   jeter2
   little Red Wagon
   school_name
   

4. Suppose your program contains the following variables and values:

     int a = 5;
     int b = 12;
     double c = 3.0;
   

   Evaluate each of the expressions below. (3 points)

     b + c
   
     a / b
   
     a + b + c
   
     a / c
   
     a + b / c
   
     (a + b) / c
   

5. Assume you have a Java program that includes the following construction of a random number generator object:

     Random r = new Random();
   

   Complete the following Java statements so that they accomplish the task as described in the preceding comment. (1 point each)

   // x should contain an integer between 0 and 999
   int x = 
   
   // y should contain an integer between 1 and 50
   int y = 
   
   // z should contain an integer between -10 and 10
   int z =
   
   // a should contain a floating-point value between 0.0 and 2.0
   double a = 
   
   // b should contain a floating-point value between 1.0 and 2.0
   double b =
   
   // c should contain a floating-point value between 10.0 and 50.0
   double c =
   

6. Convert the following Java conditional to use a switch statement that accomplishes the exact same thing. (3 points)

   if ((day == 1)||(day == 2)||(day == 3)||(day == 4)) {
       hours = 9;
   }
   else if (day == 5) {
       hours = 8;
   }
   else {
       hours = 0;
   }
   

7. Rewrite this for loop as a while loop. (3 points)

     for (int x = 0; x < 40; x += 2) {
       sum += x;
     }
   

Examples

Late penalty graph: