IteratorChain (Apache Commons Collections 3.2.2 API)

java.lang.Object
- org.apache.commons.collections.iterators.IteratorChain

All Implemented Interfaces:

Iterator
```
public class IteratorChain
extends Object
implements Iterator
```
An IteratorChain is an Iterator that wraps a number of Iterators.
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.

Since:

Commons Collections 2.1

Version:

$Revision: 972404 $ $Date: 2008-04-11 13:23:08 +0200 (Fri, 11 Apr 2008) $

Author:

Morgan Delagrange, Stephen Colebourne

Field Summary

Fields
Modifier and Type	Field and Description
`protected 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 List`	`iteratorChain` The chain of iterators
`protected 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 Summary

Constructors
Constructor and Description
`IteratorChain()` Construct an IteratorChain with no Iterators.
`IteratorChain(Collection iterators)` Constructs a new `IteratorChain` over the collection of iterators.
`IteratorChain(Iterator iterator)` Construct an IteratorChain with a single Iterator.
`IteratorChain(Iterator[] iterators)` Constructs a new `IteratorChain` over the array of iterators.
`IteratorChain(Iterator a, Iterator b)` Constructs a new `IteratorChain` over the two given iterators.

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`addIterator(Iterator iterator)` Add an Iterator to the end of the chain
`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.
`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, 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

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - iteratorChain
```
protected final List iteratorChain
```
    The chain of iterators
  - currentIteratorIndex
```
protected int currentIteratorIndex
```
    The index of the current iterator
  - currentIterator
```
protected Iterator currentIterator
```
    The current iterator
  - lastUsedIterator
```
protected Iterator lastUsedIterator
```
    The "last used" Iterator is the Iterator upon which next() or hasNext() was most recently called used for the remove() operation only
  - isLocked
```
protected boolean isLocked
```
    ComparatorChain is "locked" after the first time compare(Object,Object) is called
- Constructor Detail
  - IteratorChain
```
public IteratorChain()
```
    Construct an IteratorChain with no Iterators.
    You will normally use addIterator(Iterator) to add some iterators after using this constructor.
  - IteratorChain
```
public IteratorChain(Iterator iterator)
```
    Construct an IteratorChain with a single Iterator.
    
    Parameters:
    iterator - first Iterator in the IteratorChain
    
    Throws:
    
    NullPointerException - if the iterator is null
  - IteratorChain
```
public IteratorChain(Iterator a,
             Iterator b)
```
    Constructs a new IteratorChain over the two given iterators.
    
    Parameters:
    a - the first child iterator
    b - the second child iterator
    
    Throws:
    
    NullPointerException - if either iterator is null
  - IteratorChain
```
public IteratorChain(Iterator[] iterators)
```
    Constructs a new IteratorChain over the array of iterators.
    
    Parameters:
    iterators - the array of iterators
    
    Throws:
    
    NullPointerException - if iterators array is or contains null
  - IteratorChain
```
public IteratorChain(Collection iterators)
```
    Constructs a new IteratorChain over the collection of iterators.
    
    Parameters:
    iterators - the collection of iterators
    
    Throws:
    
    NullPointerException - if iterators collection is or contains null
    
    ClassCastException - if iterators collection doesn't contain an iterator
- Method Detail
  - addIterator
```
public void addIterator(Iterator iterator)
```
    Add 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
  - setIterator
```
public void setIterator(int index,
               Iterator iterator)
                 throws IndexOutOfBoundsException
```
    Set the Iterator at the given index
    
    Parameters:
    index - index of the Iterator to replace
    iterator - Iterator to place at the given index
    
    Throws:
    
    IndexOutOfBoundsException - if index < 0 or index > size()
    
    IllegalStateException - if I've already started iterating
    
    NullPointerException - if the iterator is null
  - getIterators
```
public List getIterators()
```
    Get the list of Iterators (unmodifiable)
    
    Returns:
    the unmodifiable list of iterators added
  - size
```
public int size()
```
    Number of Iterators in the current IteratorChain.
    
    Returns:
    Iterator count
  - isLocked
```
public boolean isLocked()
```
    Determine 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
  - updateCurrentIterator
```
protected void updateCurrentIterator()
```
    Updates the current iterator field to ensure that the current Iterator is not exhausted
  - hasNext
```
public boolean hasNext()
```
    Return true if any Iterator in the IteratorChain has a remaining element.
    
    Specified by:
    
    hasNext in interface Iterator
    
    Returns:
    true if elements remain
  - next
```
public Object next()
```
    Returns the next Object of the current Iterator
    
    Specified by:
    
    next in interface Iterator
    
    Returns:
    Object from the current Iterator
    
    Throws:
    
    NoSuchElementException - if all the Iterators are exhausted
  - remove
```
public void remove()
```
    Removes 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:
    
    remove in interface Iterator
    
    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.

Class IteratorChain

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

iteratorChain

currentIteratorIndex

currentIterator

lastUsedIterator

isLocked

Constructor Detail

IteratorChain

IteratorChain

IteratorChain

IteratorChain

IteratorChain

Method Detail

addIterator

setIterator

getIterators

size

isLocked

updateCurrentIterator

hasNext

next

remove