I just sent a couple of classes using a standard list iterator/handler
pattern from the core J2EE design patterns book to Uma.k on this list
that answer this with one solution. I will send it along to you too.
I think that when you see the code the answer to your question will
become obvious. ListHandler allows you to access members of the list
in a very sophisticated way. This is a very handy and simple design
pattern.
Jack
package com.crackwillow.list;
import java.util.Collection;
import java.util.List;
import com.crackwillow.exception.ChainedException;
public interface ListIterator {
public void setList(List list) throws ChainedException;
public Collection getList();
public int getSize() throws ChainedException;
public void setIndex(int index) throws ChainedException;
public int getCurrentIndex() throws ChainedException;
public Object getCurrentElement() throws ChainedException;
public List getPreviousElements(int count) throws ChainedException;
public List getPreviousElements() throws ChainedException;
public List getNextElements(int count) throws ChainedException;
public List getNextElements() throws ChainedException;
public void resetIndex() throws ChainedException;
} /// ;-)
package com.crackwillow.list;
import java.util.Collection;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import com.crackwillow.exception.ChainedException;
public class ListHandler
implements com.crackwillow.list.ListIterator {
static Log log = LogFactory.getLog(ListHandler.class);
private List list;
private ListIterator listIterator;
public ListHandler() {
}
public void setList(List list)
throws ChainedException {
this.list = list;
if(list != null) {
listIterator = list.listIterator();
} else {
throw new ChainedException("ListHandler: setList(List) failed:
list empty");
}
}
public Collection getList() {
return list;
}
public int getSize()
throws ChainedException{
int size = 0;
if (list != null) {
size = list.size();
} else {
throw new ChainedException("ListHandler: getList() failed"); //No Data
}
return size;
}
public void setIndex(int index)
throws ChainedException {
index -= getCurrentIndex();
int size = list.size();
if(index > size) {
throw new ChainedException("ListHandler: setCurrentIndex()
failed -- the current index chosen was greater than size)");
}
getNextElements(index);
return;
}
public int getCurrentIndex()
throws ChainedException {
// Will not advance iterator
if (list != null) {
return listIterator.nextIndex();
} else {
throw new ChainedException();
}
}
public Object getCurrentElement()
throws ChainedException {
Object obj = null;
// Will not advance iterator
if (list != null) {
int currIndex = listIterator.nextIndex();
obj = list.get(currIndex);
} else {
throw new ChainedException();
}
return obj;
}
public List getPreviousElements(int count)
throws ChainedException {
int i = 0;
Object object = null;
LinkedList list = new LinkedList();
if (listIterator != null) {
while(listIterator.hasPrevious() && (i < count)){
object = listIterator.previous();
list.add(object);
i++;
}
} else {
throw new ChainedException("ListHandler:
getPreviousElements(int) failed -- listIterator null."); // No data
}
return list;
}
public List getPreviousElements()
throws ChainedException {
Object object = null;
LinkedList list = new LinkedList();
if(listIterator != null) {
while(listIterator.hasPrevious()) {
object = listIterator.previous();
list.add(object);
}
} else {
throw new ChainedException("ListHandler: getNextElements(int)
failed -- listIterator null");
}
return list;
}
public List getNextElements(int count)
throws ChainedException {
int i = 0;
Object object = null;
LinkedList list = new LinkedList();
if(listIterator != null) {
while(listIterator.hasNext() && (i < count)) {
object = listIterator.next();
list.add(object);
i++;
}
} else {
throw new ChainedException("ListHandler: getNextElements(int)
failed -- listIterator null.");
}
return list;
}
public List getNextElements()
throws ChainedException {
Object object = null;
LinkedList list = new LinkedList();
if(listIterator != null) {
while(listIterator.hasNext()) {
object = listIterator.next();
list.add(object);
}
} else {
throw new ChainedException("ListHandler: getNextElements(int)
failed -- listIterator null");
}
return list;
}
public List getNext()
throws ChainedException {
Object object = null;
LinkedList list = new LinkedList();
if(listIterator != null) {
if(listIterator.hasNext()) {
object = listIterator.next();
list.add(object);
}
} else {
throw new ChainedException("ListHandler: getNextElements(int)
failed -- listIterator null");
}
return list;
}
public void resetIndex()
throws ChainedException{
if(listIterator != null){
listIterator = list.listIterator();
} else {
throw new ChainedException("ListHandler: resetIndex() failed --
listIterator null.");
}
}
} ///;-)
Jack
On Thu, 23 Dec 2004 13:32:07 -0500, Robert Taylor <[EMAIL PROTECTED]> wrote:
> Vinicius Caldeira Carvalho wrote:
>
> > Hi there!
> > I have a collection of beans, and this collection is set to the
> > request. I'd like to retreive only the first object of the collection
> > (later on I'll iterate over it completely) How can I do this? My
> > Collection is a List.
> > I tried <c:set var="bean" value="${collection.get(0)}">
> > and also <c:set var="bean" value="{$collection.iterator.next}">
> >
> > none of 'em seems to work. Any ideas?
> >
> > Thanks all
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: [EMAIL PROTECTED]
> > For additional commands, e-mail: [EMAIL PROTECTED]
> >
> >
> >
> You can try the following although it may not work:
>
> <c:forEach var="bean" items="collection" begin="0" end="0">
> ...
> </c:forEach>
>
> /robert
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: [EMAIL PROTECTED]
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>
>
--
------------------------------
"You can lead a horse to water but you cannot make it float on its back."
~Dakota Jack~
"You can't wake a person who is pretending to be asleep."
~Native Proverb~
"Each man is good in His sight. It is not necessary for eagles to be crows."
~Hunkesni (Sitting Bull), Hunkpapa Sioux~
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