Java ArrayIndexOutOfBounds Exception on array map

Question

I have a code that iterates on ArrayMap keys, and I got an Array Index Out Of Bounds Exception from unknown reason

From Crashalytics:

Fatal Exception: java.lang.ArrayIndexOutOfBoundsException
length=56; index=56
android.util.ArrayMap$1.colGetEntry (ArrayMap.java:763)
android.util.MapCollections$ArrayIterator.next (MapCollections.java:55)

The code looks like that:

private ArrayMap<String,RequestData> handlers = new ArrayMap<>();

public void removeAllHandlers() {
    synchronized (handlers) {
        for (String s : handlers.keySet()) {
            handlers.remove(s);
        }
    }
}

the Exception happened at this line: for (String s : handlers.keySet())

Any clue what am I doing wrong?

indices are 0 based in Java, the maximal index is 55, you are trying to retrieve the 57th element of an array with 56 elements. removing elements from a Map while iterating over the same map is asking for trouble. — Stultuske
– Stultuske, Commented Aug 14, 2018 at 8:27

Alan Deep · Accepted Answer · 2018-08-14 08:29:25Z

2

You cannot remove from a Map or a List while iterating. Use the internal clear method of the Map/List. For instance, handlers.clear();

Code:

private ArrayMap<String,RequestData> handlers = new ArrayMap<>();

public void removeAllHandlers() {
        synchronized (handlers) {
                handlers.clear();
        }
    }

answered Aug 14, 2018 at 8:29

Alan Deep

2,1151 gold badge15 silver badges22 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Ertuğrul Üngör · Accepted Answer · 2018-08-14 08:28:15Z

0

Try this

private ArrayMap<String,RequestData> handlers = new ArrayMap<>();

public void removeAllHandlers() {
    synchronized (handlers) {
        ArrayMap<String,RequestData> tempHandlers = handlers;
        for (String s : tempHandlers.keySet()) {
            handlers.remove(s);
        }
    }
}

answered Aug 14, 2018 at 8:28

Ertuğrul Üngör

2112 silver badges6 bronze badges

Comments

Faruk Yazici · Accepted Answer · 2018-08-14 08:28:33Z

0

You are modifying the ArrayMap that your are iterating over. This is an anti-pattern in Java and will cause error. I recommend you using another ArrayMap for your modifications.

answered Aug 14, 2018 at 8:28

Faruk Yazici

2,41420 silver badges41 bronze badges

Comments

Hearen · Accepted Answer · 2018-08-14 08:56:46Z

0

Just as others mentioned, you cannot remove(Object o) in a for loop, you have to do that removal using Iterator as

public void removeAllHandlers() {
    synchronized (handlers) {
            Iterator<String> keyIterator = handlers.keySet().iterator();
            while (keyIterator.hasNext()) {
                 RequestData requestData = handlers.get(keyIterator.next());
                 if(iDontWant(requestData)) {
                     keyIterator.remove();
                 }
            }
    }
}

answered Aug 14, 2018 at 8:56

Hearen

7,8864 gold badges60 silver badges74 bronze badges

Collectives™ on Stack Overflow

Java ArrayIndexOutOfBounds Exception on array map

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related