which one is better ....

[ankur rathi]

Suppose I have a list of some element and I want to retrieve the elements . So which option is much efficient and good out of this two & why ?

Iterator i = list.iterator();
while(i.hasNext()) {
System.out.println(i.next());
}

for(int i=0; i<list.size(); i++) {
System.out.println(list.get(i));
}

thanks a lot .

[Mark Spritzler]

Iterator is cleaner and easier to read.

Mark

[Bilal Al-Sallakh]

If you are using an ArrayList, it doesn't matter.
If you are using a LinkList, the Iterator is clearly more effecient.

[ankur rathi]

Why so ?

[Steven Bell]

On an ArrayList calling .get(int) is basically an index operation.
On a LinkedList calling .get(int) causes you to walk down the List starting at the first node until you get the the correct index. So you go from a O(1) operation to a O(n^2) operation. was trying to superscript the 2, didn't work

[ February 03, 2005: Message edited by: Steven Bell ]
[ February 03, 2005: Message edited by: Steven Bell ]

[Sergey Sytnik]

With Tiger u can use smth. like this:

 
public void blaBlaBla(PrintStream out) throws IOException {
   List list = getList( );
   for (Iterator i = list.iterator( ); i.hasNext( ); ) {
      Object listElement = i.next( );
      out.println(listElement.toString( ));
   }
}

or even better:

 
public void blaBlaBla(PrintStream out) throws IOException {
   List list = getList( );
   for (Object listElement:list) {
      out.println(listElement.toString( ));
   }
}

[Arul Prasad]

the best way of itreating the elements in Collection
-------------------------
Collection list = new ArrayList();

Iterator listItr = list.iterator();
int size = list.size();
for(int i = 0;i<size;i++)
{
listItr.next();
}

[ankur rathi]

why so ???

[Bilal Al-Sallakh]

Originally posted by Steven Bell:
So you go from a O(1) operation to a O(n^2) operation.

I think you he goes from an O(1) operation to an O(n) one.

[Bilal Al-Sallakh]

Originally posted by Steven Bell:
So you go from a O(1) operation to a O(n^2) operation.

I think he goes from an O(1) operation to an O(n) one.

[Bilal Al-Sallakh]

Originally posted by rathi ji:
why so ???

You may find a solid data-structures foundation in many data-structures and algorithms book. I think a good java programmer should already be familiar with them.

[Bilal Al-Sallakh]

Originally posted by rathi ji:
why so ???

You may find a solid data-structures foundation in many data-structures and algorithms book. I think a good java programmer should already be familiar with them.

[ankur rathi]

Originally posted by Arul Prasad:
the best way of itreating the elements in Collection
-------------------------
Collection list = new ArrayList();

Iterator listItr = list.iterator();
int size = list.size();
for(int i = 0;i<size;i++)
{
listItr.next();
}

why this is best ???
I think this is increasing line of code .
thanks .