CODEWITHSUNDEEP
javaiterator
Vlad Ilie
Vlad Ilie

Reputation: 1409

Improper use of foreach in java?

I'm trying to remove an item of type SubClass from an ArrayList using a foreach, and removing it right when it finds it.

The code:

for (SuperClass item : list)   
{     
     if (item instanceof SubClass)     
     {
        list.remove(item);     
     }   
}

I don't really know how the Iterator works in this case, but what I'm asking is: is this safe? Or should it throw an out of bounds exception?

Any help is appreciated!

Upvotes: 0

Views: 155

Answers (3)

Pulah Nandha
Pulah Nandha

Reputation: 774

As sanbhat say it is not safe. but what you want to do can be solve by 2 diffenret way.

1) you can store all the objects & after foreach loop you can remove by index. but it is not good way.

2) use for loop (not foreach loop) & ittrate till length. then if object found remove it. thats it.

(make sure you have written condition like i

Upvotes: 0

sanbhat
sanbhat

Reputation: 17622

You cant remove items from a list while using foreach statement. You will get ConcurrentModificationException

You need to use Iterator.remove() method

for(Iterator<SuperClass> i = list.iterator(); i.hasNext(); ) {
     SuperClass s = i.next();
     if(s instanceof SubClass) {
        i.remove();
     }
}

Upvotes: 7

newuser
newuser

Reputation: 8466

Try ListIterator:

List<SuperClass> sampleList = new ArrayList<SuperClass>();
ListIterator<SuperClass> listIterator = sampleList.listIterator();
//
listIterator.remove();
//

Upvotes: 0

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