this methods useful whenever you build dummy data using model

pick random element list java

private static <E> List<E> pickNRandomElements(List<E> list, int n, Random r) {

    int length = list.size();
    if (length < n) return null;

    //don't need to shuffle the whole list
    for (int i = length - 1; i >= length - n; --i) {
		Collections.swap(list, i, r.nextInt(i + 1));
    }
	return list.subList(length - n, length);
}

public static <E> List<E> pickNRandomElements(List<E> list, int n) {
    return pickNRandomElements(list, n, new Random());
}

/**
* how to use
*/
new ArrayList<dataType>( yourClass.pickNRandomElements( youListData, sizeOfNData ) )

//for realmList implementation
new RealmList<dataType>( yourClass.pickNRandomElements( youListData, sizeOfNData ) ).toArray( new String[yourListData.size()] )