CS 1401 Assignment #7

Due Date: correspondingly, Tuesday, October 25, 2005, or Wednesday, October 26, 2005, before the beginning of your lab section.

Goals: to practice with classes, overloading methods and handling dates.

Points: This assignment is worth a total of 20 points. No late assignments will be accepted, but credit will be given for partially completed assignments turned in on time.

Assignment: A very prominent use of computers is to maintain databases. For example, UTEP maintains all student records on databases on computers. It is a huge task to design a complete database including functionality, user interface, and considering all the security aspects. Your assignment is to design an application which implements simple student records. The steps and the desired structure are described as follows:

Step 1. Create an object-template StudentRecord class. Include the following components in the StudentRecord class:

• Define a field for each StudentRecord object to store its student ID number. The student ID is now composed of digits, but exceptionally, you may have letters or special symbols, so use the String format.
• Define two fields for each StudentRecord object to store the student's first and last name.
• Define another field for the student's address.
• Define a field for each studentRecord object to store the last date it was modified. This field is of class GregorianCalendar, a class defined in java.util. Use import java.util.*. When a GregorianCalendar is created with new without parameters, it is set to the current date. There is also the constructor of the form GregorianCalendar(int year, int month, int dayOfMonth). Months are coded from 0 to 11 instead of the usual 1 to 12.
• Define a constructor method with one parameter, the student ID number. This constructor should instantiate a student record with the string "unknown" for name and address and the current date for last date modified.
• Define accessor type methods (a get method to retrieve the value in a data field) to return the value of the individual StudentRecord fields (ID number, first and last name, address and last date modified).
• Define mutator type methods (a set method to change the value in a data field) with a value passed as an argument in order to set the value of the StudentRecord fields. In each case, except when setting the last date modified directly, reset the last date modified to the current date.
• Define a method named toString which returns a string with the value of all the StudentRecord fields in a form suitable for output to the screen. This should include the student ID number as well as the value of the other fields. For an object cal of type GregorianCalendar, accessing the year is done by cal.get(Calendar.YEAR), which returns an int. Accessing the month and date is done with the get method, using MONTH or DAY_OF_MONTH instead of YEAR. Again, be careful: the month returns an int which starts at 0 for January. You need to add 1 before converting to a String.

Step 2. Create an application class, including the following tasks:

• Instantiate one StudentRecord object using the default constructor. Supply your own student ID number.
• Call the accessor method of the StudentRecord and print to the screen the value of the student ID number field.
• Prompt the user to enter a first and last name and an address.
• Call the mutator methods of the StudentRecord and pass the user-supplied information in order to reset appropriate fields to the provided values.
• Call the accessor method of the StudentRecord again and print to the screen the updated values for the modified fields.
• Use the toString method of the StudentRecord object to print out the state (field values) of the StudentRecord object, to verify the correct settings.
• Check to make sure the tasks above are working correctly before going on to Step 3.

Step 3. Add the following overloaded methods and a helper method to the object-template class. A method overloads the original method if it has the same name but different types of parameters. Overloading allows different versions of method to be used for different situations.

• Define an overloaded constructor method with five parameters. In addition to the ID number parameter of the other method, have the first and last name, the addres and a specific date (a GregorianCalendar object) as a parameter. This constructor should instantiate a StudentRecord object with fields initialized to the provided values.
• Define overloaded mutator methods without parameters for setting the first or last name or the address fields. This should reset the field to the default "unknown" string. It should also reset the last date modified field to the current date.
• Define a facilitator (helper type) synchronization method that takes another StudentRecord object as a parameter, verifies if the student ID number is the same, and if so, check which one is the most recent by comparing their last time updated field. You can compare the dates using the get methods of Calendar as explained above, comparing the year, month and day_of_month. Alternatively. you can check through the help if there is a method to compare two calendar objects. Select "class library" from the help menu and select "Calendar". Note that GregorianCalendar objects include the time in addition to year, month and day, so the comparison result may be different when comparing two same dates with different times. Update the outdated object by using the fields from the more recent objects. Update all fields except the student ID number.

  Note: Objects of the same class can access each other's private fields directly, but do you want to do that? Enforce encapsulation by using the public accessor and mutator methods instead.

Step 4. Add the following tasks to the application class:

• Call the mutator method defined in Step 3 (the version without parameters) to reset the address field of the first StudentRecord object back to the default value, the string "unknown".
• Call the accessor method of the first StudentRecord again and print to the screen the changed value of the time field to verify that it has been reset to its default.
• Prompt the user to enter a Student ID number, last and first name, address and date (ask for date, month and year) for a second StudentRecord object and read it in.
• Instantiate a second StudentRecord object using the overloaded constructor defined in Step 3 with the user-supplied information. You will need to create an object of type GregorianCalendar and set the year, month and date using the "set" method instead of "get", with the same parameters (Calendar.YEAR, Calendar.MONTH or Calendar.DAY_OF_MONTH)
• Call the accessor method of the second StudentRecord and print to the screen the value of the date last modified to verify that the field has been set to the user provided date.
• Call the synchronization method of the first StudentRecord object to potentially update the fields of the outdated student record. When the user provides the same student ID number but a different date, the older record should be updated.
• Use the toString methods of both StudentRecord objects to print out the state of both StudentRecord objects.

For extra credit: Java provides an easy way to save and retrieve objects. Objects created in an application may be written to a file to save their current state. Afterwards, the data values may be read back in to recreate the object. This process is called serialization (translation from object to bytes in a file) and deserialization (the reverse operation). To support serialization, the object's class name must have the words "implements Serializable" following the class name to indicate that the extra functionality of the serializable interface is available for the class. The file objects used for output and input of objects are of type ObjectOutputStream and ObjectInputStream, and the associated methods are writeObject and readObject. Implement the serialization interface for the StudentRecord class, and save the current state of one of your StudentRecord objects to an output file. Read the object back in using deserialization. Refer to pp. 354-358 of the textbook for more details. Please note that you will only be given credit for the extra credit assignment if your main assignment works.

Deliverables: as announced in the labs.