> This is the "normal" behavior of an Iterator
but is it normal?
I don't want to get the same element repeatedly...
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ListIterator
In ListIterator alternating calls to next and previous will return the same element repeatedly.
Any other iterator acts "normally"? or I should implement my one iterator?
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Answers
When u was next method in a iterator, as also in ListIterator, the iterator "pops" the top element from its list. therefor the current element wil be another element - the one after it in the list. when using the previous method - the previous element to the current one is the one u just poped - the same one !
-gkern
look at thes previous method documentation:
"Returns the previous element in the list. This method may be called repeatedly to iterate through the list backwards, or intermixed withcalls to <tt>next</tt> to go back and forth. (Note that alternating calls to <tt>next</tt> and <tt>previous</tt> will return the same element repeatedly.)" - form java.util.ListIterator
"only if the previous call was next - very tricky! "
Actually, if you just keep a temporary variable for what was last retrieved from the iterator this is very easy. For example:
Object last = null;
Iterator it = xxx.iterator();
last = it.next();
Object value = it.previous();
if (last == value)
{
value = it.previous();
}
Just a rough idea, and the same concept can be applied to next calls also.
Think of your "cursor" as being between elements, not on an element. If you call next() it jumps forward over an element and returns it. If you call previous() it jumps backward over an element and returns it. Notice sequential calls to next() and previous will be jumping over the same element.
If you want to "peek" at an element without jumping over it you can use list.get(iter.nextIndex())
So:
list.get(iter.nextIndex())
list.get(iter.previousInde
will return elements on either side of the cursor. (2 separate elements.
May I suggest using a loop using the indexes of the list instead of an iterator for this type of forward and backward movement.
s_lavie:
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by: gkernPosted on 2002-12-18 at 09:13:02ID: 7602419
This is the "normal" behavior of an Iterator