ENSF-593 Assignment 2

An assignment on exploring command line and graphical user interfaces.

This assignment has two mandatory parts:

• 1. Days in month
• 2. Certificate of Deposit

and three optional parts (not graded):

• Leap Year
• Temperature GUI
• Robust Certificate of Deposit

1. Days in Month

Problem Statement

The months of the year can contain 28, 30, or 31 days. In the months preceding August (the 8th month), the odd numbered months contain 31 days and even numbered months contains 30 days, except for February (the 2nd month), which has 28 days. Beginning in August, however, the even numbered months contain 31 days and the odd numbered months 30 days. Example: September (the 9th month) has 30 days, while December (the 12th month) has 31 days. Implement a Java graphical user interface that prompts the user to enter a number which represents a month of the year, and reports whether that month contains 28, 30, or 31 days.

GUI Specification

The Graphical User Interface (GUI) for this project should correspond to the GUI interface of the stub for this lab. The following elements are present:

• The user's input should be handled with a JTextField object.
• The prompt should be handled with a JLabel object.
• The result should be reported with a JTextArea object.

Design Specifications

This program should be broken into two classes: Days and MonthJFrame.

MonthJFrame will serve as a user interface. It will prompt the user for a number and then pass that number to the Days.howManyDays(int) method , which returns an integer representing the number of days in the month. The GUI will then report the result on the screen. You will be provided with incomplete versions of both of these classes.

Complete implementation of src/MonthJFrame.java. Note the following features:

• The GUI class has 2 instance variables, a JTextField for user input, and a JTextArea to report the result.
• The constructor initializes the GUI's instance variables and adds the GUI objects to the JFrame. Note that the inputField is assigned an ActionListener to handle its actions. It is in this method that you will add code to compute and report the output to the user.
• The actionPerformed() method handles only one event: the event that occurs when the user presses the RETURN or ENTER key in the inputField. All other events are ignored. This method gets the user's input, converts it to an int and stores it in the number variable. You need to add code to call the corresponding method to calculate the number of days and update the JTextArea object with the result. Note how a String input value is converted into an int using the Integer wrapper class:

   number = Integer.parseInt( inputField.getText() );

Any value typed into a JTextField is represented as a String.

Complete implementation of src/Days.java. Note the following features:

• The Days class is modeled after the Math class. It is declared final, which means that it cannot be extended (subclassed). And its constructor is declared private, which means that this class cannot be instantiated.
• To complete this class, you must define the howManyDays(int) method. This should be public static method that takes a single int parameter and returns an integer value.
• Since howManyDays() is defined as static, it is known as a class method (rather than an instance method). It is associated with the Days class itself rather than with any of its instances. Thus, to invoke this method (in a print statement), you would use the following reference:

     System.out.println("There are " + Days.howManyDays(6)
         +" days") ...

This is similar to the way you would invoke the Math.sqrt(25) method. It is not necessary to instantiate Days in your GUI application.

Complete implementation of src/DaysTester.java. This class only has a main() method. Its purpose is to test Days class by running through all the months 1 - 12 and print the corresponding number of days as reported by Days class.

Prior starting implementation, draw a UML diagram for the MonthJFrame and Days classes.

Reporting

In the markdown file DaysInMonth.md add the UML class diagram you drew as an embedded image. Include a screenshot demonstrating successful execution and outputs of DaysTester. Include a screenshot of your final GUI and instructions for a new user to use it.

2. Certificate of Deposit

Problem Statement

The goal is to solve Exercise 5.7 and 5.8 in Java, Java, Java 3e.

From Exercise 5.7: A Certificate of Deposit (CD) is an investment instrument that accumulates interest at a given rate for an initial principal over a fixed number of years. The formula for compounding interest is shown in Table 5.11. It assumes that interest is compounded annually. For daily compounding, the annual rate must be divided by 365, and the compounding period must be multiplied by 365, giving: $a = p(1 + r/365)^{365n}$. Implement a BankCD class that calculates the maturity value of a CD.

From Exercise 5.8: Design a command-line user interface to the BankCD class that lets the user input principal, interest rate, and years, and reports the CD’s maturity value with both yearly and daily compounding. Use NumberFormat objects to display percentages and dollar figures in an appropriate format. The program’s output should look something like the following:

 ************************ OUTPUT ********************
 Compare daily and annual compounding for a Bank CD.
  Input CD initial principal, e.g.  1000.55 > 2500
  Input CD interest rate, e.g.  6.5 > 7.8
  Input the number of years to maturity, e.g., 10.5 > 5
 For Principal = $2,500.00 Rate= 7.8% Years= 5.0
  The maturity value compounded yearly is $3,639.43
  The maturity value compounded daily is: $3,692.30
 ************************ OUTPUT ********************

Specification

A file src/BankCD.java is prepared. Elements of the BankCD class are outlined in the UML in Fig 5.11 in the book. Briefly:

• Three instance variables principal, rate, years of type double.
• One constructor taking three parameters to initialize the corresponding instance variables.
• Two public methods calcYearly() and calcDaily() returning yearly and daily compound principal for the duration as a double.

The command-line interface is to be implemented in the run() method of the BankCDApp class (see src/BankCDApp.java). This class uses KeyboardReader class (already present in src/KeyboardReader.java) to prompt, read input and display to standard input and output. Once the inputs are read, calculation is performed using and instance of BankCD. Note that main() needs to instantiate an object of the BankCDApp class and call its run() method.

Prior starting implementation, draw a UML diagram showing the relationships and details of BankCD, BankCDApp and KeyboardReader classes.

Reporting

In the markdown file CertificateOfDeposit.md add the UML class diagram you drew as an embedded image. Include a screenshot demonstrating successful execution and outputs.

Optional: Leap Year

The above version of the days in month program does not handle leap years. This is important, a leap year will come up soon.

Similar to Days, add a new class Year with one static method isLeapYear(int) returning true if the year passed as argument is a leap year, false if not. A year is a leap year if it is evenly divisible by 4 but not evenly divisible by 100 unless it is also evenly divisible by 400. So 1996 was a leap year. But 1900 was not a leap year because, although it is divisible by 4, it is also divisible by 100 and not by 400. 2000 is a leap year because it is divisible by 400.

Add input elements and logic to the GUI to allow the user to enter the year in addition to the month, and report the correct number of days.

Please copy and rename any files you modify by adding 2 to the file name to not conflict with your initial files.

Optional: Temperature GUI

Solve Exercise 5.2 in Java, Java, Java 3e.

Following the design for the GUI developed in Chapter 4, implement a GUI to use for testing the Temperature class. The GUI should have the layout shown in Figure 5.7.

Optional: Robust Certificate of Deposit

The above version of the certificate of deposit application is not yet robust against a user entering wrong information. Most importantly, when asked for the principal, a user could enter some text (as string) causing the program to throw an exception. Furthermore, the program should make sure data entered is positive.

Re-design and enhance your program to guard against wrong user input. Please copy and rename any files you modify by adding 2 to the file name to not conflict with your initial files.