Why is IndexOutOfBoundsException thrown

Below code is throwing an IndexOutOfBoundsException at line Field f = getField(counter); Why is it being thrown ? Surely the field exists because I am looping based on fieldcount. Or is the list fields in the manager not gauranteed to be sequential? If this is the case how should I delete fields from a screen that are of type - MyButtonField

Thanks

        int fieldCount = getFieldCount() - 1;
        if(fieldCount > 1){
            for(int counter = 0; counter开发者_JS百科 <= fieldCount ; ++counter){
                Field f = getField(counter);
                if(f instanceof MyButtonField){                 
                    delete(f);  
                }
            }
        }

You haven't specified what delete(f) does, but if it removes it from the list of fields, then your "valid count" will effectively decrease.

To rewrite this somewhat and fix the problem:

for (int index = getFieldCount() - 1; index >= 0; index--){
    Field f = getField(index);
    if (f instanceof MyButtonField) {
        delete(f);  
    }
}

This will go from the end of the fields instead of the start, so it doesn't matter if you remove an entry and everything shuffles up - the items which shuffle up will be the ones you've already looked at.

The best way is to use Iterator for iteration then call the method remove(). Example:

        for(Iterator it = getFields().iterator();it.hasNext()){
            Field f = (Field) it.next();
            if(f instanceof MyButtonField){                 
                it.remove();  
            }
        }

The method getFields() has to return a collection of Field elements.