it.unimi.dsi.mg4j.search
Class IntervalIterators.FakeIterator

java.lang.Object
  it.unimi.dsi.fastutil.objects.AbstractObjectIterator<Interval>
      it.unimi.dsi.mg4j.search.IntervalIterators.FakeIterator

All Implemented Interfaces:

ObjectIterator<Interval>, IntervalIterator, Iterator<Interval>

Enclosing class:

IntervalIterators

protected static class IntervalIterators.FakeIterator
extends AbstractObjectIterator<Interval>
implements IntervalIterator

An iterator that throws an exception on all advancing method calls, except for hasNext(), which has a settable value. The extent is 0.

The only purpose of this class is to instantiate singleton iterators such as IntervalIterators.TRUE and IntervalIterators.FALSE.

Method Summary

int	extent() Returns an approximation of a lower bound for the length of an interval returned by this iterator.
boolean	hasNext()
void	intervalTerms(IntSet terms) Provides the set of terms that span the current interval.
Interval	next() Returns the next interval.
Interval	nextInterval() Returns the next interval provided by this interval iterator, or null if no more intervals are available.
void	reset() Resets the internal state of this iterator for a new document.
String	toString()

Methods inherited from class it.unimi.dsi.fastutil.objects.AbstractObjectIterator

remove, skip

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Iterator

remove

Method Detail

hasNext

public boolean hasNext()

Specified by:

hasNext in interface Iterator<Interval>

reset

public void reset()

Description copied from interface: IntervalIterator

Resets the internal state of this iterator for a new document.

To reduce object creation, interval iterators are usually created in a lazy fashion by document iterator when they are needed. However, this implies that every time the document iterator is moved, some internal state of the interval iterator must be reset (e.g., because on the new document some of the component interval iterators are now IntervalIterators.TRUE).

Specified by:

reset in interface IntervalIterator

next

public Interval next()

Description copied from interface: IntervalIterator

Returns the next interval.

Specified by:

next in interface IntervalIterator

Specified by:

next in interface Iterator<Interval>

See Also:

IntervalIterator.nextInterval()

nextInterval

public Interval nextInterval()

Description copied from interface: IntervalIterator

Returns the next interval provided by this interval iterator, or null if no more intervals are available.

This method has been reintroduced in MG4J 1.2 with a different semantics. The special return value null is used to mark the end of iteration. The reason for this change is providing fully lazy iteration over intervals. Fully lazy iteration does not provide an hasNext() method—you have to actually ask for the next element and check the return value. Fully lazy iteration is much lighter on method calls (half) and in most (if not all) MG4J classes leads to a much simpler logic. Moreover, IntervalIterator.nextInterval() can be specified as throwing an IOException, which avoids the pernicious proliferation of try/catch blocks in very short, low-level methods (it was having a detectable impact on performance).

Specified by:

nextInterval in interface IntervalIterator

Returns:

the next interval, or null if no more intervals are available.

extent

public int extent()

Description copied from interface: IntervalIterator

Returns an approximation of a lower bound for the length of an interval returned by this iterator.

Specified by:

extent in interface IntervalIterator

Returns:

an approximation of a lower bound for the length of an interval.

toString

public String toString()

Overrides:

toString in class Object

intervalTerms

public void intervalTerms(IntSet terms)

Description copied from interface: IntervalIterator

Provides the set of terms that span the current interval.

For each interval returned by MG4J, there is a set of terms that caused the interval to be returned. The terms appear inside the interval, and certainly at its extremes.

Note that the results of this method must be taken with a grain of salt: there might be different sets of terms causing the current interval, and only one will be returned.

Specified by:

intervalTerms in interface IntervalIterator

Parameters:

terms - a set of integers that will be filled with the terms spanning the current interval.