Yes, you can use "int". You can check the Changelog at the Assessed Lab for this error handling possibilities.

Yes, according the requirements we only have two parameters for Union, Intersection. The Complement only have single SetExpression. You can safe to assume that there are always 2 parameters for testing the Union and Intersection.

ANONYMOUS wrote Yes. Please take a look in the Assessed Lab at the Changelog section.

ANONYMOUS wrote Hi. If you think that the comment is repetitive, you can omit it on the other classes. However, I suggest you commented some of the algorithms that you implement by your own . For example how to check whether an Union or In...

As we can see in the abstract class SetExpression , the signature of the describe() function is public abstract String describe() . It means that it must RETURN a string. Because the Empty class doesn't have any properties, there...

My suggestion is that you still need to include comments even though the code is self-explanatory. Your code may seems self-explanatory to you, but it may not to others. As every class has different properties, it is a good idea to include comments to...