@GwtCompatible public abstract class AbstractIterator<T> extends UnmodifiableIterator<T>
Iterator
interface, to make this interface easier to implement for certain types of
data sources.
Iterator
requires its implementations to support querying the
end-of-data status without changing the iterator's state, using the hasNext()
method. But many data sources, such as Reader.read()
, do not expose this information; the only way to
discover whether there is any data left is by trying to retrieve it. These
types of data sources are ordinarily difficult to write iterators for. But
using this class, one must implement only the computeNext()
method,
and invoke the endOfData()
method when appropriate.
Another example is an iterator that skips over null elements in a backing iterator. This could be implemented as:
public static Iterator<String> skipNulls(final Iterator<String> in) {
return new AbstractIterator<String>() {
protected String computeNext() {
while (in.hasNext()) {
String s = in.next();
if (s != null) {
return s;
}
}
return endOfData();
}
};
}
This class supports iterators that include null elements.
Modifier and Type | Method and Description |
---|---|
boolean |
hasNext() |
T |
next() |
T |
peek()
Returns the next element in the iteration without advancing the iteration,
according to the contract of
PeekingIterator.peek() . |
remove
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
forEachRemaining
public final boolean hasNext()
public final T next()
public final T peek()
PeekingIterator.peek()
.
Implementations of AbstractIterator
that wish to expose this
functionality should implement PeekingIterator
.
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