[SOLVED] Strange behaviour by comparing EntityIds

User Code & Projects zay-es
1

I have a very strange behaviour I can not explain at all. Maybe it is just some Java related trickery I do not understand, I don’t know. Here the code

    private void updateEntity(Entity linked, Entity solved) {
        EntityId linkId = linked.get(Link.class).getLink();
        System.out.println("XXX LINKED " + linked);
        System.out.println("XXX SOLVED " + solved);
        System.out.println("YYY LINKID " + linkId + "==" + solved.getId());
        if (linkId == solved.getId()) {
            System.out.println("HEY HO!");
            solveQuests(linked, solved);
        }
    }

And the output is this

XXX LINKED Entity[EntityId[85], values=[Link[EntityId[86]], Quest[Power]]]
XXX SOLVED Entity[EntityId[86], values=[Solved, Solution[Power]]]
YYY LINKID EntityId[86]==EntityId[86]

I can not understand why the

        if (linkId == solved.getId()) {

is not true?! If it were true I would also see the “HEY HO!”
The only thing which works so far is

        if (linkId.equals(solved.getId())) {

I guess it then makes a string compare of the toString results of the both, a little backward if you ask me.

Can somebody explain me what is going on or what I do not see which is obvious to the rest of the world?!

2

Aaargh I guess I can answer the question my self. I did a instance compare I guess, if I do

        if (linkId.getId() == solved.getId().getId()) {

it works also as I here compare the long values. I guess it should be done that way.
Thanks for listening.

3

Yep, two different EntityId instances that just happened to share the same internal value.

Groovy would do the .equals() check and spoils you in these cases. :slight_smile:

4

So actually I should use equals method? Or counts this only for groovy? To be 100% sure I now use the Long value. But if equals also works and is the right choice I will use that. And in HasMaps? There I guess EntityId is fine, right?

I’m little confused …

5

EntityId has a proper .equals() method… yes, in general you should use it.

Groovy will automatically do .equals() when you use obj == obj… and then you get spoiled when you come back to Java.

Note: Java has an Objects utility class that will do the right thing for you:
if( Objects.equals(val1, val2) ) {
}

…it takes care of the null checks and so on.

1 Like