Why is insertion order not preserved in MultiMap?

Question

public class MultiMap_Test {
    public static void main(String[] args) {
        Multimap myMultimap = ArrayListMultimap.create();

          myMu         


        

Answer 1

Why is insertion order not preserved in MultiMap?

In fact, your problem is not with MultiMap but with the selected implementation. ArrayListMultimap uses a HashMap> as implementation of the backing Map>:

public static  ArrayListMultimap create() {
    return new ArrayListMultimap();
}

//...

private ArrayListMultimap() {
    super(new HashMap>());
    expectedValuesPerKey = DEFAULT_VALUES_PER_KEY;
}

And HashMap doesn't preserve the order of the insertion of the elements.