Why does using list iterator loop forever?

Question

In my code I have the following situation:

List cedolini = (List) Bean_Dati.getListaRisultati("ListaCertificazioni");

for (Iterator iterator = cedolini.iterator(); iterator.hasNext(); ) {
    System.out.println("TEST");
}

At this time the List named cedolini contains only an element that is an instance of a class named Certificazioni, I see it using the debugger.

The problem is that when the previous code is performed it enter in an infinite loop and I don't obtain a single TEST printed in the stacktrace but something like it:

TEST
TEST
TEST
TEST
TEST
TEST
....
....
....

and it still continue entering into an infinite loop.

Why? What am I missing? How can I solve this issue?

Tip: print out a more useful "debug" message in the future.

user2864740
– user2864740

2015-01-28 16:15:40 +00:00
Commented Jan 28, 2015 at 16:15 — user2864740
– user2864740, Commented Jan 28, 2015 at 16:15

Predrag Maric · Accepted Answer · 2015-01-28 16:08:08Z

8

Because you never call iterator.next(), so iterator.hasNext() will always be true.

answered Jan 28, 2015 at 16:08

Predrag Maric

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Comments

Kon · Accepted Answer · 2015-01-28 16:08:12Z

0

You are not pulling the next element from the iterator. In your loop you should call

iterator.next()

If you look at your for loop,

for (Iterator iterator = cedolini.iterator(); iterator.hasNext(); ) {

You will see that the boolean condition iterator.hasNext() will always be true if you're not taking the next element from the iterator, which will lead to your infinite loop.

answered Jan 28, 2015 at 16:08

Kon

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thedude · Accepted Answer · 2015-01-28 16:10:37Z

0

call this in your loop

iterator.next();

answered Jan 28, 2015 at 16:10

thedude

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Giulio Biagini · Accepted Answer · 2015-01-28 16:19:06Z

0

This happens because you don't update the iterator to the next element in the iteration.

It's like you to do (imagine to have an array named list):

for (int i = 0; i < list.length; )
    System.out.println("TEST");

and you don't update i: i++.

You should change your loop adding iterator.next():

for (Iterator iterator = cedolini.iterator(); iterator.hasNext(); iterator.next())
    System.out.println("TEST");

edited Jan 28, 2015 at 16:19

answered Jan 28, 2015 at 16:13

Giulio Biagini

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