Collections Framework

[Marcelo Ortega]

In Khalid's last chapter (Collections), when he talks about OPTIONAL basic operations, what exactly does he mean?

i.e
boolean add(Object obj) //said to be optional
boolean remove(Object obj) //said to be optional

[Wei-ju Wu]

Hi,

this means that these operations do not need to be fully implemented, if you have a look at the API documentation, an operation may throw UnsupportedOperationException if a concrete implementation of the List interface does not support the add(Object obj) method.

Wei-ju

[Marcelo Ortega]

So basically, every concrete implementation inherits them, but some do not support them. Correct?

[Wei-ju Wu]

Well, I would not say "inherit", but "implements" since they are interfaces. Correct is, that they do not necessarily have to be supported.