Learn-Advanced-Java/SimpleLoanCalculator.java at main · aarushinair/Learn-Advanced-Java · GitHub

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// A simple loan calculator servlet.
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.text.*;
public class RegPayS extends HttpServlet {
  double principal; // original principal
  double intRate;   // interest rate
  double numYears;  // length of loan in years
  /* Number of payments per year. You could
     allow this value to be set by the user. */
  final int payPerYear = 12;
  NumberFormat nf;
  public void doGet(HttpServletRequest request,
                    HttpServletResponse response)
    throws ServletException, IOException {
    String payStr = "";
    // Create a number format.
    nf = NumberFormat.getInstance();
    nf.setMinimumFractionDigits(2);
    nf.setMaximumFractionDigits(2);
    // Get the parameters.
    String amountStr = request.getParameter("amount");
    String periodStr = request.getParameter("period");
    String rateStr = request.getParameter("rate");
    try {
      if(amountStr != null && periodStr != null &&
         rateStr != null) {
        principal = Double.parseDouble(amountStr);
        numYears = Double.parseDouble(periodStr);
      intRate = Double.parseDouble(rateStr) / 100;
      payStr = nf.format(compute());
    }
    else { // one or more parameters missing
      amountStr = "";
      periodStr = "";
      rateStr = "";
    }
  } catch (NumberFormatException exc) {
    // Take appropriate action here.
  }
  // Set the content type.
  response.setContentType("text/html");
  // Get the output stream.
  PrintWriter pw = response.getWriter();
  // Display the necessary HTML.
  pw.print("<html><body> <left>" +
           "<form name=\"Form1\"" +
           " action=\"http://localhost:8080/" +
           "servlets-examples/servlet/RegPayS\">" +
           "<B>Enter amount to finance:</B>" +
           " <input type=textbox name=\"amount\"" +
           " size=12 value=\"");
  pw.print(amountStr + "\">");
  pw.print("<BR><B>Enter term in years:</B>" +
           " <input type=textbox name=\"period\""+
           " size=12 value=\"");
  pw.println(periodStr + "\">");
  pw.print("<BR><B>Enter interest rate:</B>" +
           " <input type=textbox name=\"rate\"" +
           " size=12 value=\"");
  pw.print(rateStr + "\">");
  pw.print("<BR><B>Monthly Payment:</B>" +
           " <input READONLY type=textbox" +
           " name=\"payment\" size=12 value=\"");
  pw.print(payStr + "\">");
  pw.print("<BR><P><input type=submit value=\"Submit\">");
  pw.println("</form> </body> </html>");
}
// Compute the loan payment.
double compute() {
  double numer;
  double denom;
  double b, e;
  numer = intRate * principal / payPerYear;
  e = -(payPerYear * numYears);
  b = (intRate / payPerYear) + 1.0;
  denom = 1.0 - Math.pow(b, e);
  return numer / denom;
}
}


/*
👋 Hi, I’m @aarushinair - Aarushi Nair (she/her/ella)
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*/