Make Iterators.peekingIterator() reuse AbstractIterator.peek() - #3847
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Currently, `Iterators.peekingIterator()` will treat `AbstractIterator` just like any other iterator, and will call `next()` to get the element, which it then stashes. This is wasteful, since `AbstractIterator` already provides a `peek()` method that is designed to be compatible with the `PeekingIterator` interface, so use it instead. `AbstractIterator` subclasses `UnmodifiableIterator`, so we can do likewise with the `PeekingIterator` forwarder. The resulting forwarder is much more lightweight than the default `Iterators.peekingIterator()` implementation.
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vztot
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Currently,
Iterators.peekingIterator()will treatAbstractIteratorjust like any other iterator, and will callnext()to get the element, which it then stashes. This is wasteful, sinceAbstractIteratoralready provides apeek()method that is designed to be compatible with thePeekingIteratorinterface, so use it instead.AbstractIteratorsubclassesUnmodifiableIterator, so we can do likewise with thePeekingIteratorforwarder. The resulting forwarder is much more lightweight than the defaultIterators.peekingIterator()implementation.