package per.mjn._08_cal;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
// 在线版简易计算器
@WebServlet("/cal")
public class CalServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("UTF-8");
resp.setContentType("text/html;charset=utf-8");
PrintWriter out = resp.getWriter();
// -----------------------------------
// 2. 接收表单中的数据
String sNum1 = req.getParameter("num1");
String op = req.getParameter("op");
String sNum2 = req.getParameter("num2");
String result = "";
if(hasLength(sNum1) && hasLength(sNum2)) {
Integer num1 = Integer.valueOf(sNum1);
Integer num2 = Integer.valueOf(sNum2);
if("+".equals(op)) {
result = num1 + num2 + "";
}
else if("-".equals(op)) {
result = num1 - num2 + "";
}
else if("*".equals(op)) {
result = num1 * num2 + "";
}
else if("/".equals(op)) {
result = num1 / num2 + "";
}
}
// System.out.println(sNum1);
// System.out.println(op);
// System.out.println(sNum2);
// 1. 输出一个计算器的界面
out.print("<form action=‘/day3/cal‘ method=‘post‘>");
out.print("<input type=‘number‘ name=‘num1‘ value=‘" + sNum1 + "‘/>");
out.print("<select name=‘op‘>");
out.print("<option>+</option>");
out.print("<option>-</option>");
out.print("<option>*</option>");
out.print("<option>/</option>");
out.print("</select>");
out.print("<input type=‘number‘ name=‘num2‘ value=‘" + sNum2 + "‘/>");
out.print("<input type=‘submit‘ value=‘ = ‘/>");
out.print("<input type=‘text‘ value=‘" + result + "‘ disabled/>");
}
private boolean hasLength(String str) {
return str != null && !"".equals(str.trim());
}
}
<!DOCTYPE html> <html> <head> <meta charset=‘UTF-8‘> <title>Insert title here</title> </head> <body> <form action=‘‘ method=‘post‘> <input type=‘number‘ name=‘num1‘/> <select name=‘op‘> <option>+</option> <option>-</option> <option>*</option> <option>/</option> </select> <input type=‘number‘ name=‘num2‘/> <input type=‘submit‘ value=‘ = ‘/> <input type=‘text‘ value=‘‘ disabled/> </form> </body> </html>
原文：https://www.cnblogs.com/mjn1/p/11469725.html