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dwjohnston
dwjohnston

Reputation: 11781

difficulty working with subList when using a list of lists

public List<List<Integer>> splitList(
        List<Integer> values) {


    List<List<Integer>> newList = new ArrayList<ArrayList<Integer>>();
    //Type mismatch: cannot convert from ArrayList<ArrayList<Integer>> to List<List<Integer>>

    while (values.size() > numValuesInClause) {
        List<Integer> sublist = values.subList(0,numValuesInClause);
        List<Integer> values2 = values.subList(numValuesInClause, values.size());   
        values = values2; 

        newList.add( sublist);
    }
    return newList;
}

I want to pass in a list of integers, and split it out in to multiple lists of less that size numValuesInClause.

I'm having difficulty with this code, with various conversions/casting between ArrayList<Integer> and List<Integer>

For example List.subList(x,y) returns a List<E>

What's the best way to work here?

The current code shown here is what makes the most sense to me, but has the compilation error shown.

Upvotes: 3

Views: 58

Answers (1)

morgano
morgano

Reputation: 17422

Use:

List<List<Integer>> newList = new ArrayList<List<Integer>>();

instead of:

List<List<Integer>> newList = new ArrayList<ArrayList<Integer>>();

The reason for this, is that you are instantiating a concrete ArrayList of a generic element List<Integer>>

Upvotes: 3

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