CODEWITHSUNDEEP
javaandroiditeratorsynchronized
Charan Pai
Charan Pai

Reputation: 2318

ConcurrentModification Exception in ArrayList

I know there are many questions asked on this but in my case i have it in a synchronised block and i am sure that nobody will be changing my array list.. But still i get this exception SOMETIMES if i am using for-each loop.. Why ?

Here is my code snippet 

    final static Object mLock = new Object();
private static ArrayList<ConnectionAndAuthCallback> mCallbacks;
private void callAuthCallbacks() {
        synchronized (mLock) {

            if (mCallbacks != null)
                for (ConnectionAndAuthCallback calback : mCallbacks) { //here i get exception
                    calback.onAuthentication(mToken, calback.intent);
                }
        }
    }

here is the code i do on Callback

@Override
            public void onAuthentication(String token, Intent intent) {
                web.loadUrl("xyz.com");
                //unregister so that we wong get any exception or some more callbacks
                SameClass.unRegisterAuthCallbacks(this); 
            }

and in Unregister function

public static void unRegisterAuthCallbacks(ConnectionAndAuthCallback callback) {
        synchronized (mLock) {

            if (mCallbacks != null)
                if (mCallbacks.contains(callback)) {
                    mCallbacks.remove(callback); // This causing problem ?? In same thread "syncronised" wont work ??
                }
        }
    }

Upvotes: 2

Views: 152

Answers (2)

Charan Pai
Charan Pai

Reputation: 2318

Answer was, In the same thread synchronised(){} wont work. Even if you think it works then there might be a dead lock.

In my case i was removing callback object from ArrayList in the same thread where i called callback.

Upvotes: 0

Ryhan
Ryhan

Reputation: 1885

You can't perform modifications on an ArrayList or remove() in this case that you are currently reading out of or looping through. Use iterators instead.

Check out this link. And this link.

Upvotes: 1

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