I'm trying to remove an object from a list using the list iterator. I've gone through the other solutions on the website and none have alleviated the error "Exception in thread "main" java.util.ConcurrentModificationException"
here is my code that is not executing :
void PatronReturn(String bookName) {
// get to beginning
while(listIterator.hasPrevious()) {
listIterator.previous();
}
while(listIterator.hasNext()){
Book b = listIterator.next();
if (listIterator.next().getBookTitle().equals(bookName)) {
//listIterator.next();
//listIterator.remove();
books.remove(b);
//listIterator.next(); //moves to next so iterator can remove previous ?
//books.remove(listIterator.next());; // TODO see if this is correct
}
}
instead of books.remove(b)
use
the reason is, that the iterator gives you the next() book, if you only remove the book from books, the iterator has the "removed" book still as next book.
it did not work in your code, because you called .next() twice, once for the book b and a second time when comparing the book title, with the next book.
You cannot remove an item whilst iterating a list, you should use .remove()
Also remove this:
This is not neccesary
instead of
books.remove(b)
try to use
You can try the above code. I think it will able to solve your problem, that you have facing that java.util.ConcurrentModificationException" error. for more reference on the error please follow the link
Do not remove an item from a list directly. Use the
remove()
method in the iterator.Your code is also flawed in that it assumes there are additional list items:
Here you call
next()
twice, yet you've only calledhasNext
once. Perhaps you meant:Finally, you can replace:
with
You can NOT remove an item from an
ArrayList
while iterating.you can either :
ListIterator
(at most once for each next())List
implementation, like CopyOnWriteArrayList, wich is garanteed never to throw anConcurrentModificationException
, but this is probably overkill in your case.