The function taglib contains the basic String functions for the JSTL functionality.

Standard Syntax:

<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>

Example:-

<%@ taglib uri="/WEB-INF/fn.tld" prefix="fn" %><%@ taglib uri="/WEB-INF/c.tld" prefix="c" %>    <c:set var="test" value="This is the test String"/>    Index of i is :- ${fn:indexOf(test, "i")}<br>    Substring Function:- ${fn:substring(test, 3,10)}<br>    Upper Case :- ${fn:toUpperCase(test)}<br>    Lower Case:- ${fn:toLowerCase(test)}<br>    Replace Function:- ${fn:replace(test,"the","a")}<br>    contains Function:- ${fn:contains(test,"the")}<br>

Output:-