Compiler error vs runtime error

[Deepa Sreedhara]

Hi,

I would like to know why does not the compiler report error about a TreeSet without Comparable implementation on user-defined classes. Why does it have to be a runtime error?

[Henry Wong]

Deepa Sreedhara wrote:
I would like to know why does not the compiler report error about a TreeSet without Comparable implementation on user-defined classes. Why does it have to be a runtime error?

As you know, it is possible to create, and then use a TreeSet that works on objects that are not Comparable. How would the compiler be able to tell how a TreeSet instance (which doesn't exist at compile time) was created so it can confirm whether non-Comparable objects are allowed?

Henry

[Deepa Sreedhara]

I did not understand the first sentence much, "As you know, it is possible to create, and then use a TreeSet that works on objects that are not Comparable."

The second sentence clarified my doubt though. Thank you.

[Henry Wong]

Deepa Sreedhara wrote:I did not understand the first sentence much, "As you know, it is possible to create, and then use a TreeSet that works on objects that are not Comparable."

You can configure a TreeSet to work with non-Comparable instances, meaning instances that don't support the Comparable interface, and it can work fine. It can work correctly, without any Runtime exceptions, assuming that you provided a Comparator when creating the TreeSet.

Henry