Performance of multiple Iterators

Question

Hi,
my question is, which alternative will be faster. I have a class and I'm running several Iterators after each other. However, the elements in the Iterators are of the same type, so there are two possibilities:
//case 1: create a new Iterator and a new MyObject each time =======
Iterator i = something.items();
while (i.hasNext()) {
     MyObject myO = (MyObject) i.next();
     // do something
Iterator i2 = something2.items();
while (i2.hasNext()) {
     MyObject myO = (MyObject) i2.next();
     // do something
Iterator i3 = something3.items();
while (i3.hasNext()) {
     MyObject myO = (MyObject) i3.next();
     // do something
//case 2: create the Iterator and object only one time and reassign it =======
MyObject myO;
Iterator i = something.items();
while (i.hasNext()) {
     myO = (MyObject) i.next();
     // do something
i = something2.items();
while (i2.hasNext()) {
     myO = (MyObject) i.next();
     // do something
i = something3.items();
while (i3.hasNext()) {
     myO = (MyObject) i.next();
     // do something
}I'd assume option 2 is better performing, but I've rarely seen it anywhere in forums or sourcecode...
Thanks for your opinions,
Bj�rn

Answer 1

I'd assume option 2 is better performing, but I've rarely seen it
anywhere in forums or sourcecode...It has nothing to do with performance; the second option just saves
a few bytes on the current stack frame (just one iterator instead of
three to store).
You can circumvent this completely by doing this:for (Iterator i= something.iterator(); i.hasNext(); ) {
   // do something with i.next()
}now you have a new iterator that shares its little part of the stack frame
with the other iterators defined local to their for-loop.
kind regards,
Jos