ExtendedList and ExtendedHash are simple
sub-classes of the SimpleList and SimpleHash
classes. These provide a small set of convenience keys that reflect
properties of the underlying List or Map
respectively, such as the size, keysets, and so on. See the
JavaDoc for all the details.
ExtendedList has a number of other convenient features. If a
TemplateListModel needs to be cached, a SimpleList
can make a copy of it. If you're using a SimpleList as a cache,
you can also give it a shelf life; its owner (e.g. a servlet) can then ask it,
before each request is processed, whether it's gotten stale, and refresh it
if necessary.
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