How to compare equality of lists of arrays with modern Java?

Question

I have two lists of arrays.

How do I easily compare equality of these with Java 8 and its features, without using external libraries? I am looking for a \"bett

Answer 1

1) Solution based on Java 8 streams:

List> first = list1.stream().map(Arrays::asList).collect(toList());
List> second = list2.stream().map(Arrays::asList).collect(toList());
return first.equals(second);

2) Much simpler solution (works in Java 5+):

return Arrays.deepEquals(list1.toArray(), list2.toArray());

3) Regarding your new requirement (to check the contained String arrays length first), you could write a generic helper method that does equality check for transformed lists:

 boolean equal(List list1, List list2, Function mapper) {
    List first = list1.stream().map(mapper).collect(toList());
    List second = list2.stream().map(mapper).collect(toList());
    return first.equals(second);
}

Then the solution could be:

return equal(list1, list2, s -> s.length)
    && equal(list1, list2, Arrays::asList);