Calculate factorial Using Recursion
After going through this example you will be understand
how you can calculate the factorial by using recursion in jsp. To
make a program on factorial, firstly it must be clear what is recursion. In a
simple language we can define recursion as a programming technique in which a
function may call itself. The key to solving recursively is to imagine that your
method does what it says.
To make a program on factorial by using recursion in
jsp we are going to design a html page named calFactorial.html which will
take the number of which you want to calculate the factorial.
The number we have entered in the html page will be
retrieved in jsp page by using the method getParameter() method of
request implicit object. Only after that the value of the number can be
calculated. Now define the method named factorial with return type of int, it
will take one input whose factorial has to be calculated. We have defined this
method inside the declaration directive. In the method we have declared
that if the input is 1 then 1 will be returned as a factorial. If the input
number is more than 1 then the factorial will be calculated by using
recursion. The output will be displayed to you by using the out implicit
object of jsp, out object is responsible for writing the content on the jsp
page.
In this program we have used following directives and
implicit objects.
Scriptlet: The main logic of the program has to
be written here.
Declaration: This is used for declaring
variables and methods. Whatever we define in a declaration directive will be
applicable in the whole page.
req: It is one of the frequenly used implicit
object. It means that this object is applicable until the request object is
present.
out: This implicit object is used to write the
content on the browser.
The code of the html page is given below.
<html>
<head>
<title>calculate factorial</title>
</head>
<body>
<p> </p>
<table border="1" cellpadding="0"
cellspacing="0" width="35%" align="center">
<tr>
<td width="100%">
<p align="center"><b>Calculate factorial</b></p>
<form method="POST" action="calFactorial.jsp">
<p align="center"><b>Enter Number:</b>
<input type="text" name="num" size="20">
<input type="submit" value="Submit" name="B1"></p>
<p> </p>
</form>
<p> </td>
</tr>
</table>
</body>
</html>
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The code of the program is given below.
<HTML>
<HEAD>
<TITLE>Using Recursion</TITLE>
</HEAD>
<BODY>
<font size="6" color ="#000080">
Calculate factorial Using Recursion</font><br>
<%
int num=Integer.parseInt(request.getParameter("num"));
%>
<%!
int factorial(int n)
{
if (n == 1) {
return n;
}
else {
return n * factorial(n - 1);
}
}
%>
<%
out.println("The factorial of " +num+" is : " + factorial(num));
%>
</BODY>
</HTML>
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Output:
Download this example.
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