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Berkeley DB
version 4.4.20

com.sleepycat.collections
Class StoredIterator

java.lang.Object
  extended bycom.sleepycat.collections.StoredIterator
All Implemented Interfaces:
Cloneable, Iterator, ListIterator

public class StoredIterator
extends Object
implements ListIterator, Cloneable

The Iterator returned by all stored collections.

While in general this class conforms to the Iterator interface, it is important to note that all iterators for stored collections must be explicitly closed with close(). The static method close(java.util.Iterator) allows calling close for all iterators without harm to iterators that are not from stored collections, and also avoids casting. If a stored iterator is not closed, unpredictable behavior including process death may result.

This class implements the Iterator interface for all stored iterators. It also implements ListIterator because some list iterator methods apply to all stored iterators, for example, previous() and hasPrevious(). Other list iterator methods are always supported for lists, but for other types of collections are only supported under certain conditions. See nextIndex(), previousIndex(), add(java.lang.Object) and set(java.lang.Object) for details.

In addition, this class provides the following methods for stored collection iterators only. Note that the use of these methods is not compatible with the standard Java collections interface.


Method Summary
 void add(Object value)
          Inserts the specified element into the list or inserts a duplicate into other types of collections (optional operation).
protected  Object clone()
          Clones this iterator preserving its current position.
 void close()
          Closes this iterator.
static void close(Iterator i)
          Closes the given iterator using close() if it is a StoredIterator.
 int count()
          Returns the number of elements having the same key value as the key value of the element last returned by next() or previous().
 StoredCollection getCollection()
          Returns the collection associated with this iterator.
 boolean hasNext()
          Returns true if this iterator has more elements when traversing in the forward direction.
 boolean hasPrevious()
          Returns true if this iterator has more elements when traversing in the reverse direction.
 boolean isReadModifyWrite()
          Returns whether write-locks will be obtained when reading with this cursor.
 Object next()
          Returns the next element in the iteration.
 int nextIndex()
          Returns the index of the element that would be returned by a subsequent call to next.
 Object previous()
          Returns the next element in the iteration.
 int previousIndex()
          Returns the index of the element that would be returned by a subsequent call to previous.
 void remove()
          Removes the last element that was returned by next or previous (optional operation).
 void set(Object value)
          Replaces the last element returned by next or previous with the specified element (optional operation).
 void setReadModifyWrite(boolean lockForWrite)
          Changes whether write-locks will be obtained when reading with this cursor.
 
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Method Detail

close

public static void close(Iterator i)
Closes the given iterator using close() if it is a StoredIterator. If the given iterator is not a StoredIterator, this method does nothing.

Parameters:
i - is the iterator to close.
Throws:
RuntimeExceptionWrapper - if a DatabaseException is thrown.

clone

protected Object clone()
Clones this iterator preserving its current position.

Returns:
a new StoredIterator having the same position as this iterator.

isReadModifyWrite

public final boolean isReadModifyWrite()
Returns whether write-locks will be obtained when reading with this cursor. Obtaining write-locks can prevent deadlocks when reading and then modifying data.

Returns:
the write-lock setting.

setReadModifyWrite

public void setReadModifyWrite(boolean lockForWrite)
Changes whether write-locks will be obtained when reading with this cursor. Obtaining write-locks can prevent deadlocks when reading and then modifying data.

Parameters:
lockForWrite - the write-lock setting.

hasNext

public boolean hasNext()
Returns true if this iterator has more elements when traversing in the forward direction. False is returned if the iterator has been closed. This method conforms to the Iterator.hasNext() interface.

Specified by:
hasNext in interface ListIterator
Returns:
whether next() will succeed.
Throws:
RuntimeExceptionWrapper - if a DatabaseException is thrown.

hasPrevious

public boolean hasPrevious()
Returns true if this iterator has more elements when traversing in the reverse direction. It returns false if the iterator has been closed. This method conforms to the ListIterator.hasPrevious() interface.

Specified by:
hasPrevious in interface ListIterator
Returns:
whether previous() will succeed.
Throws:
RuntimeExceptionWrapper - if a DatabaseException is thrown.

next

public Object next()
Returns the next element in the iteration. This method conforms to the Iterator.next() interface.

Specified by:
next in interface ListIterator
Returns:
the next element.
Throws:
RuntimeExceptionWrapper - if a DatabaseException is thrown.

previous

public Object previous()
Returns the next element in the iteration. This method conforms to the ListIterator.previous() interface.

Specified by:
previous in interface ListIterator
Returns:
the previous element.
Throws:
RuntimeExceptionWrapper - if a DatabaseException is thrown.

nextIndex

public int nextIndex()
Returns the index of the element that would be returned by a subsequent call to next. This method conforms to the ListIterator.nextIndex() interface except that it returns Integer.MAX_VALUE for stored lists when positioned at the end of the list, rather than returning the list size as specified by the ListIterator interface. This is because the database size is not available.

Specified by:
nextIndex in interface ListIterator
Returns:
the next index.
Throws:
UnsupportedOperationException - if this iterator's collection does not use record number keys.
RuntimeExceptionWrapper - if a DatabaseException is thrown.

previousIndex

public int previousIndex()
Returns the index of the element that would be returned by a subsequent call to previous. This method conforms to the ListIterator.previousIndex() interface.

Specified by:
previousIndex in interface ListIterator
Returns:
the previous index.
Throws:
UnsupportedOperationException - if this iterator's collection does not use record number keys.
RuntimeExceptionWrapper - if a DatabaseException is thrown.

set

public void set(Object value)
Replaces the last element returned by next or previous with the specified element (optional operation). This method conforms to the ListIterator.set(java.lang.Object) interface.

Specified by:
set in interface ListIterator
Parameters:
value - the new value.
Throws:
UnsupportedOperationException - if the collection is a StoredKeySet (the set returned by Map.keySet()), or if duplicates are sorted since this would change the iterator position, or if the collection is indexed, or if the collection is read-only.
IllegalArgumentException - if an entity value binding is used and the primary key of the value given is different than the existing stored primary key.
RuntimeExceptionWrapper - if a DatabaseException is thrown.

remove

public void remove()
Removes the last element that was returned by next or previous (optional operation). This method conforms to the ListIterator.remove() interface except that when the collection is a list and the RECNO-RENUMBER access method is not used, list indices will not be renumbered.

Note that for the JE product, RECNO-RENUMBER databases are not supported, and therefore list indices are never renumbered by this method.

Specified by:
remove in interface ListIterator
Throws:
UnsupportedOperationException - if the collection is a sublist, or if the collection is read-only.
RuntimeExceptionWrapper - if a DatabaseException is thrown.

add

public void add(Object value)
Inserts the specified element into the list or inserts a duplicate into other types of collections (optional operation). This method conforms to the ListIterator.add(java.lang.Object) interface when the collection is a list and the RECNO-RENUMBER access method is used. Otherwise, this method may only be called when duplicates are allowed. If duplicates are unsorted, the new value will be inserted in the same manner as list elements. If duplicates are sorted, the new value will be inserted in sort order.

Note that for the JE product, RECNO-RENUMBER databases are not supported, and therefore this method may only be used to add duplicates.

Specified by:
add in interface ListIterator
Parameters:
value - the new value.
Throws:
UnsupportedOperationException - if the collection is a sublist, or if the collection is indexed, or if the collection is read-only, or if the collection is a list and the RECNO-RENUMBER access method was not used, or if the collection is not a list and duplicates are not allowed.
IllegalStateException - if the collection is empty and is not a list with RECNO-RENUMBER access.
IllegalArgumentException - if a duplicate value is being added that already exists and duplicates are sorted.
RuntimeExceptionWrapper - if a DatabaseException is thrown.

count

public int count()
Returns the number of elements having the same key value as the key value of the element last returned by next() or previous(). If no duplicates are allowed, 1 is always returned.

Returns:
the number of duplicates.
Throws:
IllegalStateException - if next() or previous() has not been called for this iterator, or if remove() or add() were called after the last call to next() or previous().

close

public void close()
Closes this iterator. This method does not exist in the standard Iterator or ListIterator interfaces.

After being closed, only the hasNext() and hasPrevious() methods may be called and these will return false. close() may also be called again and will do nothing. If other methods are called a NullPointerException will generally be thrown.

Throws:
RuntimeExceptionWrapper - if a DatabaseException is thrown.

getCollection

public final StoredCollection getCollection()
Returns the collection associated with this iterator. This method does not exist in the standard Iterator or ListIterator interfaces.

Returns:
the collection associated with this iterator.

Berkeley DB
version 4.4.20

Copyright (c) 1996-2005 Sleepycat Software, Inc. - All rights reserved.