Enthuware

What does the last option mean. should "amount of output" be actually "number of output". By "amount of output" this means the size of output.

Anyone?

Sorry for the delay. It does imply size and that is also the intention of the option.

For the last option "both forward and include allows the caller resource to generate any amount of output."
The explanation implies that if the output has already been committed/ flushed before the forward, the forward will throw the IllegalStateException.
I think whether the output is committed before the forward and how many kilobytes of the output are not related.

The question is asking if forward allows the caller to generate any size of output. But the explanation is saying if the output has been committed , the output cannot be forwarded.

The problem is if the a certain amount of output (i.e. more than the size of the cache) has already been generated, the response would have been committed. You can't forward it to another resource anymore. Therefore, whether the output is committed before the forward and how many kilobytes of the output are indirectly related.

HTH,
Paul.

One of the correct answers was:

A call to forward() clears the output buffer before the target resource is invoked.

This sounds like the output buffer contents are deleted. Is that so, or is it better to that the output buffer is flushed?

Yes, the buffer contents are deleted not flushed. Flushed means, sent to the client.
HTH,
Paul.