Java + MongoDB: Updating fields in amount of document

Question

I am trying to update at once fields in amount of document, I want to modify "download=0" where "md5" is in the list. When I run the code, it throws an exception:

java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
    at java.util.ArrayList.rangeCheck(Unknown Source)

This is what I am doing:

//the list is an list of "md5"

List<BasicDBObject> updateCondition=new ArrayList< BasicDBObject>(list.size());  
for(int i = 0 ; i < list.size(); i++) {
    updateCondition.get(i).put("md5", list.get(i));
    DBObject updatedValue=new BasicDBObject();  
    updatedValue.put("download", 0);   
    DBObject updateSetValue=new BasicDBObject("$set",updatedValue);               
    vt_col.update(updateCondition.get(i), updateSetValue);  
}

The exception is occuring at :

 updateCondition.get(i).put("md5", list.get(i));

I want your help, thanks for helping me.

Jorge Gutiérrez Parejo · Accepted Answer · 2016-01-29 11:00:59Z

2

Debug would help you a lot here, I can't say with a 100% accuracy, but I think you updateCondition maybe is empty.

You are trying to access updateCondition(0)... but you just create it with:

new ArrayList< BasicDBObject>(list.size());

The exception is throwing cause you don't have any objects in the list still, first you have to copy the list to the updateCondition list.

Hope it helps.

answered Jan 29, 2016 at 11:00

Jorge Gutiérrez Parejo

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1 Comment

Philipp Over a year ago

This answer is correct. To elaborate on why this happens: The constructor ArrayList<T>(int initialCapacity) does not create a list with initialCapacity entries, it creates an empty list with reserved memory for initialCapacity entries. Settng the reserved capacity of a collection is a pure performance-optimization but does not do anything regarding its behavior.

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