List of Labs

Only labs submitted to CodeLab are considered; there is no other mechanism for submitting your work.

'Approval' Exercises

• Some exercises may be labelled as requiring 'Approval' both on the lab page as well as so marked in Codelab.
• Approval exercises require my approval (in addition to the usual Codelab 'correctness' checking).
• You cannot submit the exercise for approval until it has passed Codelab's tests.
  • Once you have passed CodeLab's checking, the exercise status in the Table of Contents changes to a blue check:
    
  • At that point you can immediately, you submit the exercise for approval using the corresponding button in the upper right of the Results tab in the workspace area (next to the 'Ask Your Teacher' button):
    
    • Before submitting for approval, make sure your code is properly indented, and any required documentation (comments) are included
  • CodeLab accepting the exercise does NOT automatically submit it for approval; you must do that yourself.
• I will then accept or reject the exercise; in the latter case, I will specify what I found unacceptable.
• Once you have passed the CodeLab check, the deadline is no longer relevant; i.e., even if I reject the exercise and ask for resubmission, you will not be penalized.

Exercises are marked for Approval for several reasons:

• I want to check your style / indentation / documentation
  • This is especially true at the beginning of the course
• The exercise involves something that can't be checked by Codelab
  • For example, if I ask for a specific sort algorithm; Codelab can only check that the arrays has been sorted, but not how

A Note on the Output Displayed by CodeLab

• If your submission fails CodeLabs tests, you will be presented with your output as well as the expected output
• What you will see is only the text printed by your program (and the corresponding output of a 'correct' solution).
  • In particular, you will NOT see the user input, as it was supplied by the user, and not printed by your program.
• As an example. Given the following program that prompts the user for their last and first names and prints a greeting of the form

  Hello first name last name!!
  		

  import java.util.*;
  
  public class Hello {
       public static void main(String [] args) {
            Scanner scanner = new Scanner(System.in);
  
            System.out.print("Enter last name: ");         // prompt
            String lastName = scanner.next();
            System.out.print("Enter first name: ");         // prompt
            String firstName = scanner.next();
  
            System.out.println("Hello " + firstName + " " + lastName + "!!");  // output
       }
  }
  		

  • Here is what the execution would look like if you ran the program (notice — no bold):

    Enter last name: Weiss
    Enter first name: Gerald
    Hello Gerald Weiss!!
    				

  • Here is what how the execution is displayed on the lab page (as well as in the CodeLab instructions for the exercise (notice the bold):

    Enter last name: Weiss
    Enter first name: Gerald
    Hello Gerald Weiss!!
    				

  • In both of the above cases, you see the user input entered from the keyboard. But the actual output produced by the program (i.e., the output produced from the print or println messages sent to System.out) is actually:

    Enter last name: Enter first name: Hello Gerald Weiss!!
    				

    • Notice the absence of any of the user input (that was not printed by the program's print message)
    • This is what CodeLab will display as your program's output (it will also display similar user-inputless output for the expected output).
    • This takes a bit getting used to, but since both your output and the expected output are displiayed this way it should not be too difficult for you to find the discrepancies.

How CodeLab Provides Feedback on Console and File Output

• If the exercise involves writing output to standard output or a file, errors made in that output will result in the following feedback:

  

• Scroll down to the bottom of the page (below the "Your Submission" window — or use the arrow to collapse that window), where you will find the Test Case Table where at least one of the test cases will be incorrect:

  

• Click the which will bring up the Output Comparason Table:

  

  • The text in red strikeout (fals in the above example) highlights incorrect text in your output, i.e., text that should not be there (or at least not in the location it appears). You need to fix your program so that this is NOT displayed
  • The text in green underline (tru in the above example) displays missing text in your output, i.e., text that should be at the specified location but is not present in your output. You need to fix your program so that this IS displayed

When You are Stuck, or Things Seem to be Wrong

Getting Stuck and/or Not Sure How to Proceed

You will be prompted for a message to send and I will receive it as well as complete information on your submission.

Even if you are not at the Codelab stage yet — i.e., you are still working on your program in IntelliJ — you can always copy your code from IntelliJ, paste it into the corresponding exercise in Codelab, submit it and then submit a query.

• Please use this facility for questions about your submissions. Please do not send me questions about your submissions through email … without my also receiving the information about your submission, I cannot do much to help you.
• I typically look at the queries a couple of times a day … please be patient. If you see me in class or elsewhere, feel free to let me know you sent a query.
• Often (hopefully), you will figure out the problem (and submit a correct solution) before I get back to you. I can tell this when I read the query, and will not respond in that case.

Something Seems to be Wrong With CodeLab

Of course, you can always contact me via email, and at the worst I would tell you how you could have done it through the system (for the next time). o

Sample Test Runs & A Common Novice Mistake: "Programming to the Example"

The Sample Test Run is an example execution whose purpose is to give you a sense of what the program does, as well as to show you the exact form of the output (don't forget, Codelab is very exacting in checking it's output; often even extra or missing blank spaces will cause it to complain).

Notice that the problem is not asking you to print the number 12, nor that the user is asked to enter the number 12 from the keyboard. Rather, the user is being asked to enter ANY number and it is THAT number that is to be printed. Your program must therefore be able to work regardless of whether the user entered 12 (our example data) or ANY other number. For example if the user entered 23, the output should be The number entered is 23.

(This is the whole point of the use of variables instead of hard-coded values in a program; it allows us to run the same program with different value; for the moment those values will come from the keyboard, but we will eventually learn to get them from elsewhere as well.)

Again, providing an example (i.e., the Sample Test Run) is meant to illustrate how the program works; it it NOT meant to be a specification of the program. This distinction is often a source of confusion to beginning (and sometimes, not-so-beginning) students; I have seen this mistake in 3115, and even — though rarely — in 3130. In the above example, this results in the student simply printing out the number 12 (the code to read in a number is often omitted, or the student may be sufficiently confused and put code in to read a value, and then ignored the value read in.

This error often does not reveal itself until the program is submitted to Codelab. This is because when the student runs the program in IntelliJ, they are seeing the output they are expecting (i.e., 12 in our example). However, Codelab checks the program using data other than that presented in the Sample Test Run (for example, Codelab may run the program using the numbers 23, 41, and 220; i.e., it runs the program several times, each time with a different value). What often happens in this situation is that the student sees data NOT in the Sample Test Run, and submits a query wondering why they're seeing strange values … again it's the result of Codelab testing the program on different values