[SOLVED] Com s 2270 assignment 1

The purpose of this assignment is to give you some practice with the process of implementing a class from a specification and testing whether your implementation conforms to the specification. You’ll also get some practice with modular arithmetic.

For this assignment you will implement one class, called Printer, that models pages being printed from a simple printer. The printer has a paper tray that can hold up to some maximum number of sheets of paper. The tray can be removed (in which case there are no sheets of paper available for printing) and replaced (making the sheets available for printing). Paper can be removed from and added to the tray.

 

The printer receives a print job that is associated with a document of n pages, where the number n is specified by calling the method startPrintJob. Pages are numbered 0 through (n-1). Each time a page is printed the printer advanced by one page in the document. The print job is “circular”, in the sense that after page (n-1) is printed the printer begins printing another copy of the document starting at page 0.

 

The basic operation of the printer is provided by the method printPage, whose behavior is:

At any time, the paper tray may be removed from the printer. Doing so makes the sheets available to the printer zero. The sheets available may also be zero when the sheets in the tray run out. When this is the case printPage should print no pages and should not advance to the next page.

You are not allowed to use conditional statements in this homework. That means

specifically you will lose some manual grading points if you use “if” or “if-else” statements, loops of any sort, or ternary operators (don’t worry if you don’t know what those are yet).

 

But why?

 

The purpose of this assignment is to give you practice using variables and mathematical expressions. Wouldn’t it be just as easy to use conditionals to solve this particular assignment? Perhaps, but that won’t always be the case. Professional programmers use mathematical expression every day to simplify code, make it more readable, and make it more efficient. You’re not ready yet to write code for the Linux kernel or the InnoDB database engine or the javac compiler… So, we decided to give you an easier programming assignment and artificially tie your hands (so to speak) by forcing you to implement the logic with only variables and mathematical expressions. Some day when you are adding a patch to the Linux kernel you might thank us for the practice.

 

Hints: To solve this assignment you will need to declare instance and local variables, that part of the program design is up to you. There will be a couple of places where you need to choose the larger or smaller of two numbers, which can be done with the methods Math.max() or Math.min(). For example, the Printer has a minimum and maximum allowable number of pages in the tray, from empty to full. These functions can be used to enforce the tray capacity boundaries if needed. For the wrapping (circular) behavior, you can use the mod (%) operator.

 

Yes, it is possible to solve this assignment very neatly with just what we have learned so far in class, and the challenge of doing so will make you a better programmer! You will be penalized slightly for using conditional statements, keep in mind that if you really can’t figure it out, it’s better to turn in something working than nothing at all.

This is a “regular” assignment so we are going to read your code. Your score will be based partly (about 2/3) on Gradescope’s functional tests and partly on the TA’s assessment of the quality of your code. This means you can get partial credit even if you have errors, but it also means that even if you pass all the Gradescope tests you can still lose points. Are you doing things in a simple and direct way that makes sense? Are you defining redundant instance variables? Are you using a conditional statement when you could just be using Math.min? Are you using a loop for something that can be done with integer division? Some specific criteria that are important for this assignment are:

See the “Style and documentation” section below for additional guidelines.

Roughly 15% of the points will be for documentation and code style. Here are some general requirements and guidelines:

A significant portion (but not all) of the points for this assignment are based on the gradescope autograder tests. It is not advised to wait until the last day to run the gradescope on your code.  You have an unlimited number of submissions, and unless we receive complaints from gradescope, we will not restrict the rate at which you can submit.

Do not try to “cheat” the tests by “hardcoding” your code to pass specific tests. You are expected to implement a solution that meets the specifications described in this document, the tests are only provided to gain confidence that your solution is correct. We reserve the right to add new “hidden” tests during grading and the graders will look for “hardcoding” during the manual part of the grading.

You can find the autograder for this Assignment on gradescope.  Please see the last section of this document for more information on how to submit to Gradescope.

The specification for this assignment includes this pdf along with any “official” clarifications announced on Canvas.

There is one public constructor:

      public Printer(int trayCapacity)

Constructs a new printer with the given maximum tray capacity of the number of paper sheets it can hold. Initially the tray is empty and the printer has not printed any pages.

There are the following public methods:

                  public void startPrintJob(int documentPages)

Starts a new print job to make copies of a document that is a specified page length (documentPages). Updates the next page to print as page 0 (denotes the first page of the document).

                  public int getSheetsAvailable()

Returns the number of sheets available for printing.

      public int getNextPage()

Returns the next page number of the document that will be printed.

      public int getTotalPages()

Returns the count of all pages printed by the printer since its construction.

      public void printPage()

Simulates the printer printing a page. The number pages printed is either one or zero depending on whether there is at least one sheet of paper available to the printer. Increments the total page count of the printer by the number of pages printed. Advances the next page to print by the number of pages printed (possibly wrapping around to page zero). The number of pages available to the printer and in the tray are also updated accordingly.

      public void removeTray()

Removes the paper tray from the printer; that is, makes the sheets available to the printer zero.

      public void replaceTray()

Replaces the tray in the printer; that is, makes the sheets available to the printer the same as the number of sheets in the tray.

      public void addPaper(int sheets)

Simulates removing the tray, adding the given number of sheets (up to the maximum capacity of the tray), and replacing the tray in the printer.

      public void removePaper(int sheets)

Simulates removing the tray, removing the given number of sheets (but not allowing the sheets to go below zero), and replacing the tray in the printer.

There isn’t one! Like most Java classes, this isn’t a complete program and you can’t “run” it by itself. It’s just a single class, that is, the definition for a type of object that might be part of a larger system. To try out your class, you can write a test class with a main method like the examples below in the getting started section.

Gradescope (see below) will perform a lot of functional tests, but when you are developing and debugging your code at first you’ll always want to have some simple test cases of your own (for example in a file you can create called PrinterTests.java), as in the getting started section below.

Smart developers don’t try to write all the code and then try to find dozens of errors all at once; they work incrementally and test every new feature as it’s written. Since this is our first assignment, here is an example of some incremental steps you could take in writing this class.

  public static void main(String[] args)

  {

              // create a printer

              Printer p = new Printer(100);

              System.out.println(p.getSheetsAvailable());

              System.out.println(“Expected 0”);

              p.addPaper(1);

              System.out.println(p.getSheetsAvailable());

              System.out.println(“Expected 1”);
}

(Tip: you can find code for the simple test case above, along with the others discussed in this section, in the class SimpleTests.java linked from the assignment page on Canvas.)

   Printer p = new Printer(100);

p.startPrintJob(5);

      System.out.println(p.getNextPage());
System.out.println(“Expected 0”);

      Printer p = new Printer(100);

              p.addPaper(1);

              p.startPrintJob(5);

              p.printPage();

              System.out.println(p.getNextPage());

              System.out.println(“Expected 1”);

              System.out.println(p.getTotalPages());
System.out.println(“Expected 1”);

      Printer p = new Printer(100);

      p.addPaper (1);

      p.startPrintJob(5);

      p.printPage();

 

      // try to print a page with no paper available

      p.printPage();

      System.out.println(p.getTotalPages());

      System.out.println(“Expected 1”);

     

      // add paper and try to print again

      p.addPaper(200);

      System.out.println(p.getSheetsAvailable());

      System.out.println(“Expected 100”);

      p.printPage();

      System.out.println(p.getTotalPages());

      System.out.println(“Expected 2”);

      System.out.println(p.getNextPage());
System.out.println(“Expected 2”);

For questions, please see the Piazza Q & A pages and click on the folder hw1. If you don’t find your question answered, then create a new post with your question. Try to state the question or topic clearly in the title of your post, and attach the tag hw1. But remember, do not post any source code for the classes that are to be turned in. It is fine to post source code for general Java examples that are not being turned in. (In the Piazza editor, use the button labeled “pre” to have Java code formatted the way you typed it.)

If you have a question that absolutely cannot be asked without showing part of your source code, make the post “private” so that only the instructors and TAs can see it. Be sure you have stated a specific question; vague requests of the form “read all my code and tell me what’s wrong with it” will generally be ignored.

Of course, the instructors and TAs are always available to help you. See the Office Hours section of the syllabus to find a time that is convenient for you. We do our best to answer every question carefully, short of actually writing your code for you, but it would be unfair for the staff to fully review your assignment in detail before it is turned in.

Any announcements from the instructors on Canvas that are labeled “Official Clarification” are considered to be part of the spec, and you may lose points if you ignore them. Such posts will always be posted in the Announcements section of Piazza (and emailed directly to you). (We promise that no official clarifications will be posted within 24 hours of the due date.)

Note: You will need to complete the “Academic Dishonesty policy questionnaire,” found on the Assignments page on Canvas, before the submission link will be visible to you.

Assignments are turned in by Gradescope, there is nothing to submit on Canvas.  The assignment will be called “Assignment 1” on Gradescope, and will have a deadline of 20^th September for normal submission and 22^nd September for a late penalty.  It will run a number of functional tests and report how many (and which) tests your code passed. There are many test cases so there may be an overwhelming number of error messages. Always start reading the errors at the top and make incremental corrections in the code to fix them.  Please submit just the file called Printer.java, and at the top, there should be a line that puts it in the hw1 package, that is, “package hw1;”.  Do not create or submit any zipfiles with Gradescope even though gradescope may offer you the chance to submit a zipfile.  Zipfiles created by speccheckers (just in case that is what you have) are not in the format that Gradescope expects.  So just submit the Printer.java file as is, by itself.   Please note that any 5% bonus for early submission or 10% penalty for late submission will not be calculated by Gradescope itself.  Instead, it will be calculated by a separate script later.  So you will only see your raw score once the Teaching Assistants have graded your work.