commented, calculating interests

git-svn-id: svn://anubis/gvsu@74 45c1a28c-8058-47b2-ae61-ca45b979098e

cs621/proj3/AmortizedLoan.java

@@ -1,12 +1,31 @@
 
+/**
+ * AmortizedLoan provides a concrete implementation of a Loan object.
+ */
 public class AmortizedLoan extends Loan
 {
+    /**
+     * This constructor simply calls the contructor from the Loan class.
+     */
     public AmortizedLoan(String name, double rate, int years, double amount)
     {
         super(name, rate, years, amount);
     }
 
+    /* Return the loan type as a string */
+    public String toString()
+    {
+        return "Full Amortized Loan";
+    }
+
+    /**
+     * Calculate the monthly payment for a AmortizedLoan
+     */
     public void calcMonthlyPayment()
     {
+        double adjMonthlyRate = m_interestRate / 100.0 / 12.0;
+        double lengthInMonths = m_length * 12;
+        double n = Math.pow(1 + adjMonthlyRate, lengthInMonths);
+        m_monthlyPayment = (m_principal * adjMonthlyRate * n) / (n - 1);
     }
 }

cs621/proj3/Loan.java

@@ -1,4 +1,9 @@
 
+/**
+ * This class provides a base class for loan types.
+ * It uses the "template" design pattern where extending concrete
+ * classes can override their own specific functionality.
+ */
 public abstract class Loan
 {
     protected String m_name;
@@ -7,6 +12,13 @@ public abstract class Loan
     protected double m_principal;
     protected double m_monthlyPayment;
 
+    /**
+     * Construct a Loan object
+     * @param name the name of the loanee
+     * @param rate the interest rate of the loan
+     * @param years the length of the loan in years
+     * @param amount the initial principal of the loan
+     */
     public Loan(String name, double rate, int years, double amount)
     {
         m_name = name;
@@ -15,16 +27,39 @@ public abstract class Loan
         m_principal = amount;
     }
 
+    /**
+     * process() will calculate the monthly payment of the loan
+     * @return a summary of the loan
+     */
     public String process()
     {
         calcMonthlyPayment();
         return makeSummary();
     }
 
+    /**
+     * calcMonthlyPayment will calculate the monthly payment for the loan.
+     * It is abstract and so implementing classes will have to provide
+     * a definition for this method.
+     */
     public abstract void calcMonthlyPayment();
 
+    /**
+     * makeSummary will create a textual description of the loan
+     * @return a summary of the loan in text form
+     */
     public String makeSummary()
     {
-        return "Summary!";
+        return String.format(
+            "%s for %s%n" +
+            "%-16s: $%,.2f%n" +
+            "%-16s: %.2f%n" +
+            "%-16s: %d years%n" +
+            "%-16s: $%,.2f%n",
+            toString(), m_name,
+            "Principal", m_principal,
+            "Interest Rate", m_interestRate,
+            "Length of Loan", m_length,
+            "Monthly Payment", m_monthlyPayment);
     }
 }

cs621/proj3/LoanApplication.java

@@ -1,11 +1,19 @@
 
 import java.io.*;
 
+/**
+ * LoanApplication is the main class for creating a loan and calculating payments.
+ */
 public class LoanApplication
 {
     private Loan m_loan;
     private String m_summary;
 
+    /**
+     * The run method provides a simple command-line interface loop.
+     * It continually prompts for information for creating a new loan
+     * and displays the summary of each loan entered.
+     */
     public void run()
     {
         PrintSpooler spooler = PrintSpooler.getSpooler();
@@ -43,6 +51,7 @@ public class LoanApplication
                     ? new SimpleLoan(name, rate, years, principal)
                     : new AmortizedLoan(name, rate, years, principal);
 
+                System.out.println("");
                 spooler.printDocument(loan.process());
             }
         }

cs621/proj3/PrintSpooler.java

@@ -1,8 +1,16 @@
 
+/**
+ * A class implementing the "singleton" design pattern for printing.
+ */
 public class PrintSpooler
 {
+    /* The reference to the single PrintSpooler object
+     * that will be used to print */
     private static PrintSpooler spooler;
 
+    /**
+     * This method returns the singleton to use for printing documents.
+     */
     public static PrintSpooler getSpooler()
     {
         if (spooler == null)
@@ -10,6 +18,10 @@ public class PrintSpooler
         return spooler;
     }
 
+    /**
+     * Print a document
+     * @param s the document (string) to print
+     */
     public void printDocument(String s)
     {
         System.out.println(s);

cs621/proj3/Project3.java

@@ -1,6 +1,13 @@
 
+/**
+ * Project3 is a driver class for the LoanApplication system.
+ */
 public class Project3
 {
+    /**
+     * The main method is called when the user first starts the program.
+     * @param args any command-line arguments
+     */
     public static void main(String[] args)
     {
         LoanApplication la = new LoanApplication();

cs621/proj3/SimpleLoan.java

@@ -1,12 +1,30 @@
 
+/**
+ * SimpleLoan provides a concrete implementation of a Loan object.
+ */
 public class SimpleLoan extends Loan
 {
+    /**
+     * This constructor simply calls the contructor from the Loan class.
+     */
     public SimpleLoan(String name, double rate, int years, double amount)
     {
         super(name, rate, years, amount);
     }
 
+    /* Return the loan type as a string */
+    public String toString()
+    {
+        return "Simple Interest Loan";
+    }
+
+    /**
+     * Calculate the monthly payment for a SimpleLoan
+     */
     public void calcMonthlyPayment()
     {
+        double adjMonthlyRate = m_interestRate / 100.0 / 12.0;
+        double lengthInMonths = m_length * 12;
+        m_monthlyPayment = (m_principal * (adjMonthlyRate * lengthInMonths + 1)) / lengthInMonths;
     }
 }