[arbsn]

Surely the purpose of the LabStack example is to restrict the interface of a LinkedList to that of a Stack? Defining a new type to present a more restricted interface is not useless... it helps one reason about what has or hasn't been done to an object.

[DSMan195276]

I agree - Defining a 'Stack' class is useful even if it's just a wrapper over LinkedList, because stacks have an expected way to act, and while a LinkedList fits the bill it does more then a stack actually has to do. And with that, nothing says you have to implement a 'Stack' with a LinkedList, it's just an easy way to do it. By defining the 'Stack' class, you could always go back and improve it to not use LinkedList and instead do it yourself.

That said, I do agree with the author that, in the context of a programming class, writing the 'LabStack' class is absolutely useless because it teaches you nothing about actually using a linked-list to implement a stack, which I'm sure was the real intent of the assignment. The 'LabStack' class is useful in the context of being used in a larger program, it's not really useful for learning how to actually implement a stack because it just passes the implementation off to 'LabStack'. (That said, because Java doesn't support defining objects as value-types, using the 'LabStack' interface adds an extra level of indirection you may want to avoid - You have to access 'this.list' to get the LinkedList object, instead of just accessing it directly. This is more a fault of Java then anything else though.).

The note about programming class isn't really relevant to programming as a whole though, which is where the disconnect happens.

[xxs]

Unless the stack has to be lock free, array backed ones (ArrayDeque in java) are better on the current hardware.