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Calculator in Servlets

Summary

This is a simple Calculator developed using Java Servlets, so it uses the form type in html & uses regex for validating the numerical values.

Code

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/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package calc;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.regex.*;

/**
*
* @author Administrator
*/
public class Calculator extends HttpServlet {

/**
* Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();

/**
*
*[-+]? : Says whether it starts with + or - sign which should be allowed.
*[0-9]* : Says it can have more than one numerical digit.
*
*/
Pattern p = Pattern.compile("^[-+]?[0-9]*");
try {
/* TODO output your page here*/
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet Calculator</title>");
out.println("</head>");
out.println("<body>");


out.println("<h1>Servlet Calculator</h1><br/>");
out.println("<form value='Calculator'>");
out.println("<table border ='0'><tr>");
out.println("<td>Enter A:</td><td><input type='text' name='a' /></td></tr>");
out.println("<td>Enter B:</td><td><input type='text' name='b' /></td></tr>");
out.println("<td>Enter Operation:</td><td><input type='text' name='op' /></td></tr>");
out.println("<td><input type='submit' /></td></tr>");
out.println("</table>");
out.println("</form>");
String A = request.getParameter("a");
String B = request.getParameter("b");
/**
*
* Using Matcher it matches with our pattern mentioned earlier
*
*/
Matcher ma = p.matcher(A);
Matcher mb = p.matcher(B);
String op = request.getParameter("op");
if (ma.matches() && mb.matches()) {
if (!op.equals("") && A != null && B != null) {
double a = Double.parseDouble(A);
double b = Double.parseDouble(B);
if (op.equals("add")) {
out.println("Answer: <b>" + (a + b) + "</b>");
} else if (op.equals("sub")) {
out.println("Answer: <b>" + (a - b) + "</b>");
} else if (op.equals("mul")) {
out.println("Answer: <b>" + (a * b) + "</b>");
} else if (op.equals("div")) {
out.println("Answer: <b>" + (a / b) + "</b>");
} else {
out.println("Answer: <font color='RED'>Invalid Operation</font>");
}
} else {
out.println("Answer: <font color='CYAN'><b>Some Values are empty</b></font>");
}
} else {
out.println("Answer: <font color='DARKRED'>Invalid Values</font>");
}
out.println("</body>");
out.println("</html>");
} finally {
out.close();
}
}

/**
* Handles the HTTP <code>GET</code> method.
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);


}

/**
* Handles the HTTP <code>POST</code> method.
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);


}

/**
* Returns a short description of the servlet.
* @return a String containing servlet description
*/
@Override
public String getServletInfo() {
return "Short description";

}// </editor-fold>
}