When I try to modify a collection while iterating through it, will result in ConcurrentModification exception (i.e., when using forEach and forEachRemaining)
But below code won't why?
List<String> list=new ArrayList<>();
list.add("ram");
list.add("ravi");
Iterator<String> it=list.iterator();
while(it.hasNext()){
System.out.printing(it.next());
it.remove();
}
You ask why
List<String> list = new ArrayList<>();
Iterator<String> it = list.iterator();
while(it.hasNext()) {
System.out.printing(it.next());
}
does not throw a CCME.
The answer is simple. A CCME is thrown if you modify a list while iterating it. You are iterating the list, but you are not modifying it at the same time. Therefore the condition for throwing a CCME is not satisfied.
(The same reasoning applies in the case of a non-empty list too ...)
Let me break it down for you. You said:
When I try to modify a collection while iterating through it, will result in ConcurrentModification exception.
(This is correct as a general statement, by the way. But not universally.)
Reducing that to simple propositional logic we get:
exception_thrown = iterating_collection AND modifying_collection
In your example
iterating_collection is TRUE
modifying_collection is FALSE
but
TRUE AND FALSE is FALSE
therefore
exception_thrown is FALSE
In English, CCME is not thrown.
Now for your updated code:
List<String> list = new ArrayList<>();
list.add("ram");
list.add("ravi");
Iterator<String> it = list.iterator();
while (it.hasNext()) {
System.out.printing(it.next());
it.remove();
}
In this case, you are modifying the collection using the iterator. This is the one situation where you are allowed to modify a collection while iterating it.
Think about it. If Iterator.remove() was not permitted to remove an element from the collection that is being iterated, it would be a fundamentally useless operation!
