org.eclipse.gemini.blueprint.service.importer.support.internal.collection

Class DynamicCollection.DynamicIterator

java.lang.Object

org.eclipse.gemini.blueprint.service.importer.support.internal.collection.DynamicCollection.DynamicIterator

All Implemented Interfaces:

java.util.Iterator<E>

Direct Known Subclasses:

DynamicList.DynamicListIterator

Enclosing class:

DynamicCollection<E>

protected class DynamicCollection.DynamicIterator
extends java.lang.Object
implements java.util.Iterator<E>

Dynamic consistent iterator. This iterator is not thread-safe with respect to iteration (it should not be shared against multiple threads) but it is thread safe with respect to the backing storage which might be modified during the iterator life cycle.

Field Summary

Fields

Modifier and Type	Field and Description
protected int	cursor Cursor pointing to the element that has to be returned by next() method.
protected java.lang.Boolean	hasNext Iterator variable - not thread-safe/synchronized since only one thread should use the iterator.
protected java.lang.Object	lock Lock protecting the cursor and tailGhost which might be affected by the backing collection shrinking.
protected boolean	removalAllowed Iterator variable - not thread-safe/synchronized since only one thread should use the iterator.
protected E	tailGhost Temporary object holder.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	DynamicIterator()

Method Summary

Modifier and Type	Method and Description
boolean	hasNext()
E	next()
protected int	removalIndex(int cursor)
void	remove()
(package private) void	removeObject(int index, E o) Removes the object from the underlying collection.
protected boolean	unsafeHasNext() Updates the hasNext field.

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

Field Detail

cursor

protected volatile int cursor

Cursor pointing to the element that has to be returned by next() method. This element needs to be synchronized.

tailGhost

protected volatile E tailGhost

Temporary object holder. Used in case the last element in the collection becomes empty after an iterator #hasNext() method was called but before #next() is invoked since otherwise the iterator needs to return an element but it cannot. Subclasses (such as lists) should implement their own strategy when it comes to assign a value to it to accommodate the collection semantics (ordered vs indexed). This particular field represents the tail of the collection, since no order or indexing is enforced and the iteration can only go forward. The field is assigned when an object is removed and resetted by calls to hasNext() or next(). Thread-safety note: Since this object is affected by the storage shrinking it needs to be synchronized.

lock

protected final java.lang.Object lock

Lock protecting the cursor and tailGhost which might be affected by the backing collection shrinking.

hasNext

protected java.lang.Boolean hasNext

Iterator variable - not thread-safe/synchronized since only one thread should use the iterator.

removalAllowed

protected boolean removalAllowed

Iterator variable - not thread-safe/synchronized since only one thread should use the iterator.

Constructor Detail

DynamicIterator

protected DynamicIterator()

Method Detail

hasNext

public boolean hasNext()

Specified by:

hasNext in interface java.util.Iterator<E>

unsafeHasNext

protected boolean unsafeHasNext()

Updates the hasNext field. Internal unprotected method to avoid nested synchronization blocks. To execute this code, one needs the storage, iteratorsLock and iterator lock.

Returns:

next

public E next()

Specified by:

next in interface java.util.Iterator<E>

remove

public void remove()

Specified by:

remove in interface java.util.Iterator<E>

removalIndex

protected int removalIndex(int cursor)

removeObject

void removeObject(int index,
                  E o)

Removes the object from the underlying collection. This operation is relevant to the iterators since it can occur in between hasNext()/next() calls. If no object is left, next() is forced to return null which can contradict the hasNext() contract. For such a case, the iterator is forced to temporarily recall the last available object.

Parameters:

index -

o -