SE-0010 Introduction to Java
Lab 2: Interest Calculator

Outcomes

• Develop additional proficiency with the Java language
• Develop further proficiency using common Java classes, such as Math, SImpleDateFormat, DecimalFormat, etc.
• Program mathematical expressions and formulas using the Java Math package
• Use methods of the String class to manipulate String data
• [Optional] Incorporate conditional control statements, such as if and switch, into a Java program to affect program control flow.

For this assignment, you will write a program that computes the value of an interest-bearing CD (Certificate of Deposit) over a period of time. The initial value of the CD, the interest rate, and the period of time will all be determined by asking the user for those values.

Your program will consist of a single InterestCalculator class. For this assignment, this will be the only class needed. Within this class, you'll use several methods, as follows:

main method - this is the usual method where your program begins to execute when it is run, from within this method, you'll print a JOptionPane-based welcome screen, and after that, you'll call the following methods:

getInitialValue - this is a method that prompts the user for the initial value of the CD, converts that input to a numerical value, and returns that value to main().

getInterestRate - this is a method that prompts the user for the annual interest rate of the CD, converts that input to a numerical value, and returns that value to main().

getInterval - this is a method that prompts the user for the intervals (in years) at which the compounded value of the CD will be computed; it converts that input to a numerical value, and returns that value to main()

computeCDValue - this is the method that computes the value of the CD at a certain period of time (in years) after the original purchase. This method expects three arguments: the original purchase price of the CD, the annual interest rate, and the number of years since the CD was purchased. It computes the compounded value and returns that value to main(). From main(), you'll call this method 5 times, computing the value at 5 different intervals after purchase and storing the results in five different variables. For example, if the user entered 3 as the interval value, then you'll compute and store the CD compounded values at 3, 6, 9, 12, and 15 years after the original purchase date.

displayResults - this is the method that displays the results of the computations. This method expects five arguments: the five computed results of the compounded values of the CD at the five intervals. This method returns nothing back to main().

After you display the results, your program should end.

Detailed requirements

• Your program is to present to the user a JOptionPane-based welcome message stating what it does and what it will ask the user for in terms of information, similar to that shown below:
  
   
• Your program must prompt the user for three pieces of information:
   
  1. The purchase price of the CD. You must accept a value such as 1000.00, representing $1000.00.
     
      
  2. The interest rate which the CD bears. You must accept a value such as 7.6, representing 7.6%.
     
      
  3. The year-intervals at which the compounded value of the CD will be computed. You must accept a value such as 3, representing 3 years.
     
      
• If interest on the CD is compounded daily, the formula for calculating the compunded value of the CD is given by
  
  where V_c is the current value,
  V_i is the initial value,
  I is the annual percentage rate (note that I is 0.076 if the interest rate is 7.6%),
  n is the number of days (not years) since the purchase of the CD. Assume every year has 365 days (which is not exactly true, but it's close enough).
   
• You must use JOptionPane.showMessageDialog to output the information in a neatly formatted fashion. The output should appear as follows (example output is for a $1000 CD bearing 5% interest, computed for five 2-year intervals):
  
   
• You must output the monetary value with 2 decimal places of precision, as shown above.
   
• [Optional] When the user enters the purchase price of the CD, you should ensure that the value is greater than 0, and if it is not, inform the user of the error via a JOptionPane-based dialog  that informs the user that the purchase price must be specified as a value greater than 0.0.
   
• [Optional] When the user enters the interest rate for the CD, you must ensure that the value is greater than 0 and less than 100, and if it is not, inform the user of the error via a JOptionPane-based dialog that informs the user that the interest rate must be specified as a value between 0.0 and 100.0.
   
• [Optional] When the user enters the year-interval for computing the compounded values, you must ensure that the value is greater or equal to 1 and less than or equal to 10, and if it is not, inform the user of the error via a JOptionPane-based dialog that informs the user that the year-interval must be specified as a value between 1 and 10.
   
• [Optional] In all error cases, after you display the message dialog, you should terminate the program by calling System.exit(0).

Test your program and make certain that it works correctly; use the results shown above to verify your output.

Remember: This is an individual assignment. While you may discuss the concepts with your classmates, you must write your own program. You may not copy or borrow code from your classmates.

Lab Submission (due 8:00am, Tuesday following lab)

Be sure to keep a copy of your work, in case something gets lost.

Your grade will be based on the following criteria:

• Meeting requirements - that is, a working Java program..
• Technical quality of both your program. For the program, technical quality consists of formatting, commenting, and following coding style guidelines we discussed in lectures and the textbook.
• Spelling and grammar (in comments).
• Timeliness of submission as stated in the course policies.