CODEWITHSUNDEEP
javacollectionsiterator
user3817287
user3817287

Reputation: 139

(java) remove in iterator cannot be applied

I am trying to remove some objects from a List while iterating over the list. To avoid, ConcurrentModificationException, I am using an Iterator and calling remove(). This part of the code looks like the following.

  Iterator<ClassName> it = classList.iterator();

    while(it.hasNext()) {
        ClassName obj = it.next();
        if(obj.getData() == 1) {
            it.remove(obj);
        }
    }

I get the following error: remove() in java.util.Iterator cannot be applied to (ClassName). I have two questions

  1. Why do I get this compilation error and how to fix it?
  2. Is it a good practice (or even safe) to remove objects from a list while iterating over the list?

Upvotes: 0

Views: 1797

Answers (6)

sol4me
sol4me

Reputation: 15698

The method remove doesn't take any arguments , try

it.remove();

There is no harm in removing object while iterating from the List if you are using Iterator but calling directly myList.remove(obj/index) can result in ConcurrentModificationException. Care should be taken when you are in multi-threaded environment.

Upvotes: 0

Suresh Atta
Suresh Atta

Reputation: 121998

Why do I get this compilation error and how to fix it?

You need not to pass an object to it. Current object will be remove directly. it.remove() is enough

Is it a good practice (or even safe) to remove objects from a list while iterating over the list?

Yes. That is fine to iterate and remove an element from it. What not good practice/safe is removing directly from list object instead of iterator. When you try to remove from list directly and looping on it, that leads to ConcurrentModificationException.

Upvotes: 0

Mohammad Ashfaq
Mohammad Ashfaq

Reputation: 1373

Try it.remove() as mentioned by many Answers, and yes you can remove the objects and it is safe to remove while iterating over list.

Upvotes: 0

Shoaib Chikate
Shoaib Chikate

Reputation: 8975

There is no method of iterator which takes arguements as object.

 Iterator<ClassName> it = classList.iterator();

    while(it.hasNext()) {
        ClassName obj = it.next();
        if(obj.getData() == 1) {
            it.remove();
        }
    }

Iterator.remove() is safe.

Note that Iterator.remove is the only safe way to modify a collection during iteration; the behavior is unspecified if the underlying collection is modified in any other way while the iteration is in progress.

is from:

http://docs.oracle.com/javase/tutorial/collections/interfaces/collection.html

Upvotes: 0

Ruchira Gayan Ranaweera
Ruchira Gayan Ranaweera

Reputation: 35547

You should call remove() in iterator which takes no arguments.

Iterator<ClassName> it = classList.iterator();

while(it.hasNext()) {
    ClassName obj = it.next();
    if(obj.getData() == 1) {
        it.remove();
    }
}

Yes iterator is the way to remove object while iterating.

Upvotes: 0

aioobe
aioobe

Reputation: 420921

1. Why do I get this compilation error and how to fix it?

Do it.remove() (and don't give it any arguments). The method will remove the current object from the underlying collection.

2. Is it a good practice (or even safe) to remove objects from a list while iterating over the list?

Yes. This is a perfectly fine way to remove objects from a collection.

Upvotes: 2

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