Question

Obviously, sets do not have any kind of ordering, so I cannot expect any specific ordering if I do

String[] string = mySet.toArray();

However, I am faced with a use case where I don’t care what ordering the string array is in, but I DO need it to be the case that if two sets are equal to each other, then:

StringUtils.join(mySet.toArray(),',');

will produce the same exact string for those sets, always, no matter how many times I run the program assuming I stick with the same code.

Do I have this guarantee?

Similarly, does this whole true for the order that elements appear for a given Set in an iterator?

Answer 1

Technically, no you don’t have a guarantee. Set is an Interface. Implementations will vary and may or may not obey this requirement.

Force the issue by sorting the array yourself after extracting the results from the Set.