compare two Sets

[kri shan]

How to compare Set<Custom-Object> with Set<String>.


Set<Custom-Object> set1 = foo();

set1 has sunday and monday (2 values)


Set<String> set2 = new HashSet<>();
set2.add("sunday");
set2.add("monday");


set1.equals(set2) returns false.

[Campbell Ritchie]

How on earth will a set of custom objects be equal to a set of Strings? Unless they are both empty.

[Paweł Baczyński]

Well, maybe OP didn't mean equal by the means of equals() method.
Maybe OP meant equal defined as: for every entry in custom-object-set (name it entry) check if there is entry.toString() in the string-set. Maybe.
We can not know for sure until OP clarifies the requirements.

[Stephan van Hulst]

Assuming Paweł's assumption, I would probably map-collect the first set to a new set of Strings, and then compare that to the second set.

[Campbell Ritchie]

Agree. If Paweł is correct about this new meaning for equality, that would work.

[salvin francis]

As for the actual comparison, Set.containsAll() method might be helpful (given that you just want to see that all elements in one set is contained in another) or simply equals() method (I haven't tried it for a set)
However, as others have pointed out it does not make sense to compare two objects if they represent something else.

Its like saying i want to compare Set<Zombies> with Set<Zebras>