Re: HashMap and Array issue
teser3@hotmail.com wrote:
I have this JSP where I have alot of fields with conditions.
I would like to make it more efficient and use a for loop.
Here is an example (showing 2 fields for example only):
<%@ page language="java" import="java.util.*" %>
<%
HashMap errors = new HashMap();
String firstname = "Joe";
String lastname = "Miller";
if (!firstname.equals(""))
{
errors.put("firstname",firstname);
}
if (!lastname.equals(""))
{
errors.put("lastname",lastname);
}
out.println(errors.get("firstname"));
out.println(errors.get("lastname"));
%>
It prints out Joe Miller
Now my attempt below to put this in a loop prints out null null:
<%@ page language="java" import="java.util.*" %>
<%
HashMap errors = new HashMap();
or better: Map errors = new HashMap();
String firstname = "Joe";
String lastname = "Miller";
String[] keys = {firstname, lastname};
This array contains {"Joe", "Miller"}
for(int i = 0;i < keys.length;i++)
{
if(!keys[i].equals(""))
{
errors.put(keys[i],keys[i]);
This will insert the <K, V> pairs <"Joe", "Joe"> and <"Miller", "Miller"> into
the Map.
You're using the exact same value for both the key and the value of each
Map.Entry.
}
}
out.println(errors.get("firstname"));
A better idiom is
<%= errors.get( "firstname" ) %>
"firstname" was never entered into the Map as a key, only "Joe" and "Miller".
out.println(errors.get("lastname"));
"lastname" was never entered into the Map as a key, only "Joe" and "Miller".
%>
After you get the hang of doing this in a JSP, figure out how to move all Java
source out of the JSP and into logic classes invoked from a servlet.
--
Lew