CODEWITHSUNDEEP
javalistloopscollectionsiterator
user4296472
user4296472

Reputation:

Why does using list iterator loop forever?

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?

Upvotes: 1

Views: 615

Answers (4)

Giulio Biagini
Giulio Biagini

Reputation: 920

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");

Upvotes: 0

thedude
thedude

Reputation: 51

call this in your loop

iterator.next();

Upvotes: 0

Kon
Kon

Reputation: 10810

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.

Upvotes: 0

Predrag Maric
Predrag Maric

Reputation: 24403

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

Upvotes: 8

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