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Using of [ ] operator with the ArrayList

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EL expressions are always used within curly braces, and prefixed with a dollar($) sign and $(expression).

Using [ ] operator with the ArrayList

        

EL expressions are always used within curly braces, and prefixed with a dollar($) sign and $(expression). The first named variable in the expression is either an implicit object or an attribute stored in one of the the four scopes i.e. page, request, session, or application. The [] operator is much more powerful than the dot, because it lets you access Map key or a bean property name as well as the access to arrays and Lists.

ArrayList is resizable array implementation of the List interface. As the elements are increased in an ArrayList, its capacity also grows automatically. It can store all type of elements including null. In ArrayList,  if you have to access the first value of the list by using the EL, we can retrieve it by using ${list["0"]} or ${list[0]}. EL doesn't care about if you have put quotes around the list index or not. If you don't put quotes inside the brackets, the web container evaluates it and gives you the result. If it is in quotes, and also not an index into an array or List, then the container sees it as the literal name or a property or a key.

We have made a program on ArrayList by using the EL, in which we are going to retrieve the values of the arraylist, firstly by setting the attribute and thereafter retrieving the values of the arraylist by using the key associated with the ArrayList.

The code of the program is given below:

<%@ page import = "java.util.*"%>
<% ArrayList al = new ArrayList();
al.add("This is EL");
al.add("We are using the [] operator");
al.add("It gives you more options than dot(.) operator");
request.setAttribute("al", al);
%>
<body>
	<center>
	<table>
	<tr><td><h3>First Value in arraylist is : ${al[0]}</h3></td></tr><br>
	<tr><td><h3>Second value in arraylist is : ${al["1"]}</h3></tr></td>
	<tr><td><h3>Third value in arraylist is : ${al["2"]}</h3></tr></td>
	</table>
	</center>
</body>

The output of the program is given below:

Download this example.

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Posted on: April 18, 2011

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Comments
Shubham
February 25, 2013
how to use [] when the index is another variable

my question is how do we print the arraylist element when the index is another variable? eg. <td><c:out value="${PARENT_MODULE[module.moduleId]}"> </c:out></td> here.. module.moduleId is a variable. Thanks
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