Iterator.next() is ignored for List<Value<T>>

[volgin]

This code produces an endless loop:

List<Value<Long>> releases = entity.getList("releases");
System.out.println(releases.size());    // prints 1 

while (releases.iterator().hasNext()) {
    Value<Long> value = releases.iterator().next();
    System.out.println(value.get());   // prints correct value over and over
}

[ajkannan]

The condition in the while loop creates a new iterator for each iteration of the loop, which causes the infinite loop. If you save the iterator you create before the while loop rather than creating a new one each time, the problem should be fixed.

[volgin]

Is this documented? Typically I don't expect a new iterator created when I simply pass a reference to it.

-----Original Message-----
From: "Ajay Kannan" notifications@github.com
Sent: ‎5/‎6/‎2016 6:57 PM
To: "GoogleCloudPlatform/gcloud-java" gcloud-java@noreply.github.com
Cc: "volgin" volgin@spiraluniverse.com; "Author" author@noreply.github.com
Subject: Re: [GoogleCloudPlatform/gcloud-java] Iterator.next() is ignored forList<Value> (#993)

The condition in the while loop creates a new iterator for each iteration of the loop, which causes the infinite loop. If you save the iterator you create before the while loop rather than creating a new one each time, the problem should be fixed.
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[ajkannan]

releases is of type java.util.List (which is Iterable). The contract of Iterable's iterator() is to return a new iterator over all items in the list. The code you provide would also loop endlessly if you used some other generic type (e.g. Integer), like below:

List<Integer> releases = Collections.singletonList(1);
System.out.println(releases.size());

while (releases.iterator().hasNext()) {
    int value = releases.iterator().next();
    System.out.println(value);
}

[volgin]

OK. Thank you for a quick response, and feel free to close this issue.