de.thaw.comb.util

Class MutableIterator<E>

java.lang.Object

de.thaw.comb.util.MutableIterator<E>

All Implemented Interfaces:

Iterator

public class MutableIterator<E>
extends Object
implements Iterator

An Iterator behaving like a FIFO queue. Adheres to the general contract of the Iterator interface, but offers methods to safely append items to the iterator while the iteration is ongoing.

This iterator/queue does not support null elements (for performance reasons).

Author:

Arne Johannessen

Constructor Summary

Constructors

Constructor and Description
MutableIterator() Creates a new instance as empty FIFO queue.

Method Summary

Modifier and Type	Method and Description
void	add(E item) Appends the offered element to the tail of this queue.
void	addAll(Collection<? extends E> items) Appends the offered elements to the tail of this queue (in the order they are returned by their iterator).
boolean	hasNext() Returns true if the iteration has more elements.
E	next() Retrieves and removes the head of this queue.
void	remove() Always throws an UnsupportedOperationException.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Iterator

forEachRemaining

Constructor Detail

MutableIterator

public MutableIterator()

Creates a new instance as empty FIFO queue. In this initial state, hasNext() returns false and next() throws an exception. Use add(Object) to append items to the queue.

Method Detail

add

public void add(E item)

Appends the offered element to the tail of this queue.

Throws:

NullPointerException - iff item == null

addAll

public void addAll(Collection<? extends E> items)

Appends the offered elements to the tail of this queue (in the order they are returned by their iterator).

Throws:

NullPointerException - if any of the elements are null

See Also:

Collection.iterator()

hasNext

public boolean hasNext()

Returns true if the iteration has more elements. (In other words, returns true if next would return an element rather than throwing an exception.)

If this method returns false, it means that the queue is currently empty. Even after calls to hasNext() or next() have returned false or thrown NoSuchElementExceptions, respectively, it is allowed to use add(Object) and addAll() to append some more elements to the queue. At that point, this method will once again return true and calling next() will work as expected.

Specified by:

hasNext in interface Iterator

Returns:

true if the iterator has more elements

next

public E next()

Retrieves and removes the head of this queue.

Specified by:

next in interface Iterator

Returns:

the head of this queue

Throws:

NoSuchElementException - if this queue is currently empty

remove

public void remove()

Always throws an UnsupportedOperationException.

Because of this class's queue-like character, a call to next() automatically removes the element returned from the backing collection. (This happens internally, the collection(s) used to initialise this instance are not affected.) The Iterator.remove() method being specified to remove the last element previously returned by calling next(), calling this method would mean to remove it twice. It throws an exception instead of just doing nothing for forward compatibility.

Specified by:

remove in interface Iterator

Throws:

UnsupportedOperationException