mock exam example

[dolly shah]

Set set = new TreeSet();
set.add("F");
set.add("B");
set.add("E");
set.add("A");
int count=0;
while(set.iterator().hasNext()){
System.out.print(set.iterator().next()+" ");
count++;
if(count==3)break;
}

How the result of above code is A A A. They have given the description "The program output will output A A A because when set.iterator() is called it returns a new iterator object. Each time the loop runs it creates and examines a new iterator object, but never advances beyond the first item. If we didn't break out of the loop after three iterations it would go on forever." But I am not getting it. Can anyone please explain?

[Brian Cole]

Does it make more sense if I rewrite it like this?

Set set = new TreeSet();
set.add("F");
set.add("B");
set.add("E");
set.add("A");
int count=0;
Iterator itA = set.iterator();
while(itA.hasNext()){
Iterator itB = set.iterator();
System.out.print(itB.next()+" ");
count++;
if(count==3)break;
}

The point is not only that itB is different from itA, but that itB is fleeting. It exists for one iteration of the loop, then is gone. A brand new itB gets created on the next iteration.

[edit: transient -> fleeting (no reason to create confusion with the transient keyword)]
[ August 30, 2007: Message edited by: Brian Cole ]