Class IteratorChain<E>
- Type Parameters:
- E- the type of elements in this iterator.
- All Implemented Interfaces:
- Iterator<E>
This class makes multiple iterators look like one to the caller. When any method from the Iterator interface is called, the IteratorChain will delegate to a single underlying Iterator. The IteratorChain will invoke the Iterators in sequence until all Iterators are exhausted.
Under many circumstances, linking Iterators together in this manner is more efficient (and convenient) than reading out the contents of each Iterator into a List and creating a new Iterator.
Calling a method that adds new Iterator after a method in the Iterator interface has been called will result in an UnsupportedOperationException.
NOTE: As from version 3.0, the IteratorChain may contain no iterators. In this case the class will function as an empty iterator.
 NOTE: As from version 4.0, the IteratorChain stores the iterators in a queue
 and removes any reference to them as soon as they are not used anymore. Thus,
 the methods setIterator(Iterator) and getIterators() have been
 removed and size() will return the number of remaining iterators in
 the queue.
 
- Since:
- 2.1
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Constructor SummaryConstructorsConstructorDescriptionConstructs an IteratorChain with no Iterators.IteratorChain(Collection<? extends Iterator<? extends E>> iteratorQueue) Constructs a newIteratorChainover the collection of iterators.IteratorChain(Iterator<? extends E> iterator) Constructs an IteratorChain with a single Iterator.IteratorChain(Iterator<? extends E>... iteratorQueue) Constructs a newIteratorChainover the array of iterators.IteratorChain(Iterator<? extends E> first, Iterator<? extends E> second) Constructs a newIteratorChainover the two given iterators.
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Method SummaryModifier and TypeMethodDescriptionvoidaddIterator(Iterator<? extends E> iterator) Add an Iterator to the end of the chainbooleanhasNext()Return true if any Iterator in the IteratorChain has a remaining element.booleanisLocked()Determine if modifications can still be made to the IteratorChain.next()Returns the next Object of the current Iteratorvoidremove()Removes from the underlying collection the last element returned by the Iterator.intsize()Returns the remaining number of Iterators in the current IteratorChain.protected voidUpdates the current iterator field to ensure that the current Iterator is not exhaustedMethods inherited from class java.lang.Objectclone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, waitMethods inherited from interface java.util.IteratorforEachRemaining
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Constructor Details- 
IteratorChainpublic IteratorChain()Constructs an IteratorChain with no Iterators.You will normally use addIterator(Iterator)to add some iterators after using this constructor.
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IteratorChainConstructs a newIteratorChainover the collection of iterators.This method takes a collection of iterators. The newly constructed iterator will iterate through each one of the input iterators in turn. - Parameters:
- iteratorQueue- the collection of iterators, not null
- Throws:
- NullPointerException- if iterators collection is or contains null
- ClassCastException- if iterators collection doesn't contain an iterator
 
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IteratorChainConstructs an IteratorChain with a single Iterator.This method takes one iterator. The newly constructed iterator will iterate through that iterator. Thus calling this constructor on its own will have no effect other than decorating the input iterator. You will normally use addIterator(Iterator)to add some more iterators after using this constructor.- Parameters:
- iterator- the first child iterator in the IteratorChain, not null
- Throws:
- NullPointerException- if the iterator is null
 
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IteratorChainConstructs a newIteratorChainover the array of iterators.This method takes an array of iterators. The newly constructed iterator will iterate through each one of the input iterators in turn. - Parameters:
- iteratorQueue- the array of iterators, not null
- Throws:
- NullPointerException- if iterators array is or contains null
 
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IteratorChainConstructs a newIteratorChainover the two given iterators.This method takes two iterators. The newly constructed iterator will iterate through each one of the input iterators in turn. - Parameters:
- first- the first child iterator in the IteratorChain, not null
- second- the second child iterator in the IteratorChain, not null
- Throws:
- NullPointerException- if either iterator is null
 
 
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Method Details- 
addIteratorAdd an Iterator to the end of the chain- Parameters:
- iterator- Iterator to add
- Throws:
- IllegalStateException- if I've already started iterating
- NullPointerException- if the iterator is null
 
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hasNext
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isLockedDetermine if modifications can still be made to the IteratorChain. IteratorChains cannot be modified once they have executed a method from the Iterator interface.- Returns:
- true if IteratorChain cannot be modified, false if it can
 
- 
next
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removeRemoves from the underlying collection the last element returned by the Iterator. As with next() and hasNext(), this method calls remove() on the underlying Iterator. Therefore, this method may throw an UnsupportedOperationException if the underlying Iterator does not support this method.- Specified by:
- removein interface- Iterator<E>
- Throws:
- UnsupportedOperationException- if the remove operator is not supported by the underlying Iterator
- IllegalStateException- if the next method has not yet been called, or the remove method has already been called after the last call to the next method.
 
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sizeReturns the remaining number of Iterators in the current IteratorChain.- Returns:
- Iterator count
 
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updateCurrentIteratorUpdates the current iterator field to ensure that the current Iterator is not exhausted
 
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