For iterator to delete items in array

Question

I wrote this little method to delete all items in a array with a specific value:

   public void removeNote2(String r){
         for(String file : notes){
             if(file == r){
                 notes.remove(r);
             }
         }
    }

Somehow i always get this error:

java.util.ConcurrentModificationException
    at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:859)
    at java.util.ArrayList$Itr.next(ArrayList.java:831)
    at Notebook.removeNote2(Notebook.java:63)

What did i wrong? And what do i have to change?

First `if(file == r)` is not good. Use equals to compare content of Strings. Second google for `ConcurrentModificationException`. — Alexis C., Nov 23 '13 at 18:48
You are removing while iterating. Using Iterator.remove() instead. — Peter Lawrey, Nov 23 '13 at 18:49

score 2 · Accepted Answer · answered Nov 23 '13 at 18:49

You cannot iterate the list and remove items from it the way you're trying to do. It leads to ConcurrentModificationException. The proper way to do this, is to use iterator:

Iterator<String> iterator = notes.iterator();
while(iterator.hasNext()) {
  String file = iterator.next();
  if (file == r)
    iterator.remove();
}

Btw, you'll probably want to use equals() when comparing strings, not ==.

score 1 · Answer 2 · answered Nov 23 '13 at 18:55

1

In Java 8, do this:

notes.removeIf(file -> file.equals(r));

answered Nov 23 '13 at 18:55

Stuart Marks

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For iterator to delete items in array

2 Answers2