JSTL fn:length() Function

In JSTL, the fn:length() function is mainly used to specify the length or size of a collection, array, or string in JSP. This function returns the number of elements in the given object as input.

Used to retrieve the size or length information within the JSTL expressions.
The fn:length() function is part of the JSTL core tag library.

In this article, we will see the syntax, parameters, and example of the fn:length() function.

Syntax of fn:length()

${fn:length(String inputString/Collection object)}

Where,

${fn:length(...)}: This is the JSTL expression for getting the length or size.
String inputString: This is the paramter passed to the length function. The length function retrins the length of the spcifiec string.
Collection object: This is the paramter passed to the length function. The length fuction retrins the number of elements in the collection.

Example of JSTL fn:length() Function

In this example, we see how to find the length of a string using the JSTL fn:length() Function.

HTML

<%@ page contentType="text/html;charset=UTF-8" language="java" %> 
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> 
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %> 

<html> 

  <head> 

      <title>JSTL fn:length() example</title> 

  </head> 

  <body> 

    <c:set var="inputString" value="GeeksforGeeks"/> 

    <c:set var="stringList" value="${fn:split('Geeks for Geeks', ' ')}"/> 

    <p>Length of the String: ${fn:length(inputString)}</p> 

    <p>Length of the Collection: ${fn:length(stringList)}</p> 

  </body> 

</html>

Output:

Length of the String: 13
Length of the Collection: 3

Output Screen of the above Program:

Explanation of the above Program:

In the above example, we initialized the inputString with “GeeksforGeeks” and stringList by spitting “Geeks for Geeks” spaces.
Here, the ${fn:length(inputString)} evaluates to the length of the string stored in the variable inputString and prints the output as 13 using <p> tag.
The ${fn:length(stringList)} calculates the number of elements in the collection stringList, which is created by splitting the string ‘Geeks for Geeks‘ at spaces. This returns and pints the length as 3.

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