How to find the index of an arraylist in an arraylist?

Question

I have an ArrayList of ArrayLists of T, and I am trying to find the index of the ArrayList that contains a certain object

private int indexOfItem(T item)
{
    int index = 10000;

    for(int i = 0; i < bigList.size(); i++)
    {
        if(bigList.get(i).contains(item))
        {
            index = i;
        }

    }
    return index;
}

this works but is there a better way to do this using the indexOf() method that arrayLists have?

Why do you return 10000 by default? Why not some impossible value like -1 instead? indexOf() would return the index of a list that is equal to item, and that is obviously not possible. because a list of items is never equal to an item. — JB Nizet
– JB Nizet, Commented Apr 4, 2016 at 18:52

petey · Accepted Answer · 2016-04-04 20:15:57Z

1

That is exactly what indexOf does with one exception: As soon as you find the item, you can stop looking:

private int indexOfItem(T item) {
  for(int i = 0; i < bigList.size(); i++) {
    if(bigList.get(i).contains(item)) {
      return i;
    }
  }
  return -1;
}

edited Apr 4, 2016 at 20:15

petey

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answered Apr 4, 2016 at 18:49

f1sh

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