import java.io.*;
import java.util.Scanner;

/*********************************************************************
*
* @author Duncan Buell
*/
public class Loan
{
  private double payoff,principal,rate;

/*********************************************************************
* This is the standard constructor, which ought for good form do the
* explicit initialization of the instance variables for the class. 
*/
  public Loan()
  {
    this.payoff = 0.0;
    this.principal = 0.0;
    this.rate = 0.0;
  } // public Loan()

/*********************************************************************
* This method simply returns the double precision value of the 
* monthly payoff.
*
* @return The double value that is the monthly loan payoff.
*/
  public double getPayoff()
  {
    return(this.payoff);
  }

/*********************************************************************
* This method simply returns the double precision value of the current
* loan principal.
*
* @return The double value that is the current loan principal.
*/
  public double getPrincipal()
  {
    return(this.principal);
  }

/*********************************************************************
* This method simply returns the double precision value of the loan
* interest rate.
*
* @return The double value that is the loan interest rate.
*/
  public double getRate()
  {
    return(this.rate);
  }

/*********************************************************************
* This method takes an input string, converts to a double, and sets
* that double value as the monthly payoff amount of the loan.
* It SHOULD be the case that extensive error testing is done in this
* method to determine that in fact the input string represents a legal
* value for a double.  However, we don't do that here.
*
* @param The (String) value of what is supposed to be a double.
* @return A boolean false of the input was illegal, else true.
*/
  public boolean setPayoff(String inString)
  {
    boolean returnValue;
    double convertedValue;

    convertedValue = Double.valueOf(inString);
    returnValue = false;
    if(convertedValue > 0.0)
    {
      this.payoff = convertedValue;
      returnValue = true;
    }

    return(returnValue);
  }

/*********************************************************************
* This method takes an input string, converts to a double, and sets
* that double value as the prinicpal amount of the loan.
* Same comments about error checking as for the payoff.
*
* @param The (String) value of what is supposed to be a double.
* @return A boolean false of the input was illegal, else true.
*/
  public boolean setPrincipal(String inString)
  {
    boolean returnValue;
    double convertedValue;

    convertedValue = Double.valueOf(inString);
    returnValue = false;
    if(convertedValue > 0.0)
    {
      this.principal = convertedValue;
      returnValue = true;
    }

    return(returnValue);
  }

/*********************************************************************
* This method takes an input string, converts to a double, and sets
* that double value as the interest rate of the loan.
* Same comments about error checking as for the payoff.
*
* @param The (String) value of what is supposed to be a double.
* @return A boolean false of the input was illegal, else true.
*/
  public boolean setRate(String inString)
  {
    boolean returnValue;
    double convertedValue;

    convertedValue = Double.valueOf(inString);
    returnValue = false;
    if(convertedValue > 0.0)
    {
      this.rate = convertedValue;
      returnValue = true;
    }

    return(returnValue);
  }

/*********************************************************************
* This method amortizes the loan until the principal balance is zero.
* NOTE: This assumes monthly calculation of interest, without regard
* to the number of days in a month, etc.
*/
  public void amortize()
  {
    int month;
    double interestThisMonth,newPrincipal;

    System.out.printf("Mon OldPrinc     Int  NewPrinc%n");
    month = 0;
    while(this.principal > 0.0)
    {
      ++month;
      interestThisMonth = this.principal * (this.rate/100.0) / 12.0;
      newPrincipal = this.principal + interestThisMonth - this.payoff;
      System.out.printf("%3d %8.2f %8.2f %8.2f %n",month,principal,interestThisMonth,newPrincipal);
      this.principal = newPrincipal;

      if(month > 180) System.exit(0);
    }
  } // public void amortize()

} // public class Loan