/*
 * File: CDInterest.java
 * Author: Java, Java, Java
 * Description:  This application program illustrates the use of Java library
 *  classes to perform certain useful calculations.

 *  It uses the java.lang.Math class to calculate the principal of a
 *  Certificate  of Deposit (CD) invested at a certain interest rate for a certain
 *  time period. It uses the java.text.NumberFormat class to format the numerical results
 *  which represent dollar amounts and percentages.
 */

import java.io.*;                // Import the Java I/O Classes
import java.text.NumberFormat;   // For formatting as $nn.dd or n%

public class CDInterest {
    private BufferedReader input = new BufferedReader	// Handles console input
                 (new InputStreamReader(System.in));
    private String inputString;                   // Stores the input
    private double principal;                     // The CD's initial principal
    private double rate;                          // CD's interest rate
    private double years;                         // Number of years to maturity
    private double cdAnnual;         // Accumulated principal with annual compounding
    private double cdDaily;          // Accumulated principal with daily compounding

    /**
     *  convertStringTodouble() converts a String of the form "54.87" into
     *  its corresponding double value (54.87).
     *  @param s -- stores the string to be converted
     *  @return A double is returned
     */
    private double convertStringTodouble(String s) {
        Double doubleObject = Double.valueOf(s) ;
        return doubleObject.doubleValue();
    }

    /**
     *  getInput() handles all the input required by the program. It inputs
     *   three Strings and converts each to a (double) number, storing them
     *   in instance variables (principal, rate, and years).
     */
    private void getInput() throws IOException {
                                                 // Prompt the user and get the input
        System.out.println("This program compares daily and annual compounding for a CD.");

        System.out.print("     Input the CD's initial principal, e.g. 1000.55 > ");
        inputString = input.readLine();
        principal = convertStringTodouble(inputString);

        System.out.print("     Input the CD's interest rate, e.g. 6.5 > ");
        inputString = input.readLine();
        rate = (convertStringTodouble(inputString)) / 100.0;

        System.out.print("     Input the number of years to maturity, e.g., 10.5 > ");
        inputString = input.readLine();
        years = convertStringTodouble(inputString);
    } //getInput()

    /**
     *  calcAndReportResults() handles all the interest calculations and reports
     *   the program's results. Note the use of Math.pow() to calculate the CD's
     *   value, and the use of the NumberFormat.format() methods for making the output
     *   look pretty.
     */
    private void calcAndReportResult() {
                                                // Calculate and output the result
        NumberFormat dollars = NumberFormat.getCurrencyInstance(); // Set up formats
        NumberFormat percent = NumberFormat.getPercentInstance();
        percent.setMaximumFractionDigits(2);

        cdAnnual = principal * Math.pow(1 + rate, years);        // Calculate interest
        cdDaily = principal * Math.pow(1 + rate/365, years*365);
                                                               // Print the results
        System.out.println("The original principal is " + dollars.format(principal));
        System.out.println("The resulting principal compounded daily at " +
                       percent.format(rate) + " is " + dollars.format(cdDaily));
        System.out.println("The resulting principal compounded yearly at " +
                       percent.format(rate) + " is " + dollars.format(cdAnnual));
    } // calcAndReportResult()

    /**
     *   main() creates an instance of the CDInterest object and then invokes
     *    its methods to calculate the interest for a CD using values input by
     *    the user.
     */
    public static void main( String args[] ) throws IOException {
        CDInterest cd = new CDInterest();
        cd.getInput();
        cd.calcAndReportResult();
    } // main()
} // Interest