public class IteratorChain
extends java.lang.Object
implements java.util.Iterator
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 Iteratorafter a method in the Iterator interface has been called will result in an UnsupportedOperationException. Subclasses should take care to not alter the underlying List of Iterators.
NOTE: As from version 3.0, the IteratorChain may contain no iterators. In this case the class will function as an empty iterator.
Modifier and Type | Field and Description |
---|---|
protected java.util.Iterator |
currentIterator
The current iterator
|
protected int |
currentIteratorIndex
The index of the current iterator
|
protected boolean |
isLocked
ComparatorChain is "locked" after the first time
compare(Object,Object) is called
|
protected java.util.List |
iteratorChain
The chain of iterators
|
protected java.util.Iterator |
lastUsedIterator
The "last used" Iterator is the Iterator upon which
next() or hasNext() was most recently called
used for the remove() operation only
|
Constructor and Description |
---|
IteratorChain()
Construct an IteratorChain with no Iterators.
|
IteratorChain(java.util.Collection iterators)
Constructs a new
IteratorChain over the collection
of iterators. |
IteratorChain(java.util.Iterator iterator)
Construct an IteratorChain with a single Iterator.
|
IteratorChain(java.util.Iterator[] iterators)
Constructs a new
IteratorChain over the array
of iterators. |
IteratorChain(java.util.Iterator a,
java.util.Iterator b)
Constructs a new
IteratorChain over the two
given iterators. |
Modifier and Type | Method and Description |
---|---|
void |
addIterator(java.util.Iterator iterator)
Add an Iterator to the end of the chain
|
private void |
checkLocked()
Checks whether the iterator chain is now locked and in use.
|
java.util.List |
getIterators()
Get the list of Iterators (unmodifiable)
|
boolean |
hasNext()
Return true if any Iterator in the IteratorChain has a remaining element.
|
boolean |
isLocked()
Determine if modifications can still be made to the IteratorChain.
|
private void |
lockChain()
Lock the chain so no more iterators can be added.
|
java.lang.Object |
next()
Returns the next Object of the current Iterator
|
void |
remove()
Removes from the underlying collection the last element
returned by the Iterator.
|
void |
setIterator(int index,
java.util.Iterator iterator)
Set the Iterator at the given index
|
int |
size()
Number of Iterators in the current IteratorChain.
|
protected void |
updateCurrentIterator()
Updates the current iterator field to ensure that the current Iterator
is not exhausted
|
protected final java.util.List iteratorChain
protected int currentIteratorIndex
protected java.util.Iterator currentIterator
protected java.util.Iterator lastUsedIterator
protected boolean isLocked
public IteratorChain()
You will normally use addIterator(Iterator)
to add
some iterators after using this constructor.
public IteratorChain(java.util.Iterator iterator)
iterator
- first Iterator in the IteratorChainjava.lang.NullPointerException
- if the iterator is nullpublic IteratorChain(java.util.Iterator a, java.util.Iterator b)
IteratorChain
over the two
given iterators.a
- the first child iteratorb
- the second child iteratorjava.lang.NullPointerException
- if either iterator is nullpublic IteratorChain(java.util.Iterator[] iterators)
IteratorChain
over the array
of iterators.iterators
- the array of iteratorsjava.lang.NullPointerException
- if iterators array is or contains nullpublic IteratorChain(java.util.Collection iterators)
IteratorChain
over the collection
of iterators.iterators
- the collection of iteratorsjava.lang.NullPointerException
- if iterators collection is or contains nulljava.lang.ClassCastException
- if iterators collection doesn't contain an iteratorpublic void addIterator(java.util.Iterator iterator)
iterator
- Iterator to addjava.lang.IllegalStateException
- if I've already started iteratingjava.lang.NullPointerException
- if the iterator is nullpublic void setIterator(int index, java.util.Iterator iterator) throws java.lang.IndexOutOfBoundsException
index
- index of the Iterator to replaceiterator
- Iterator to place at the given indexjava.lang.IndexOutOfBoundsException
- if index < 0 or index > size()java.lang.IllegalStateException
- if I've already started iteratingjava.lang.NullPointerException
- if the iterator is nullpublic java.util.List getIterators()
public int size()
public boolean isLocked()
private void checkLocked()
private void lockChain()
protected void updateCurrentIterator()
public boolean hasNext()
hasNext
in interface java.util.Iterator
public java.lang.Object next()
next
in interface java.util.Iterator
java.util.NoSuchElementException
- if all the Iterators are exhaustedpublic void remove()
remove
in interface java.util.Iterator
java.lang.UnsupportedOperationException
- if the remove operator is not supported by the underlying Iteratorjava.lang.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.