com.sleepycat.collections

Class StoredIterator

public class StoredIterator extends Object implements BaseIterator, 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 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, StoredIterator and StoredIterator. Other list iterator methods are always supported for lists, but for other types of collections are only supported under certain conditions. See StoredIterator, StoredIterator, StoredIterator and StoredIterator 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
voidadd(Object value)
Inserts the specified element into the list or inserts a duplicate into other types of collections (optional operation).
static voidclose(Iterator i)
Closes the given iterator using close if it is a StoredIterator.
voidclose()
Closes this iterator.
intcount()
Returns the number of elements having the same key value as the key value of the element last returned by next() or previous().
ListIteratordup()
StoredCollectiongetCollection()
Returns the collection associated with this iterator.
booleanhasNext()
Returns true if this iterator has more elements when traversing in the forward direction.
booleanhasPrevious()
Returns true if this iterator has more elements when traversing in the reverse direction.
booleanisCurrentData(Object currentData)
booleanisReadModifyWrite()
Returns whether write-locks will be obtained when reading with this cursor.
booleanmoveToIndex(int index)
Objectnext()
Returns the next element in the iteration.
intnextIndex()
Returns the index of the element that would be returned by a subsequent call to next.
Objectprevious()
Returns the next element in the iteration.
intpreviousIndex()
Returns the index of the element that would be returned by a subsequent call to previous.
voidremove()
Removes the last element that was returned by next or previous (optional operation).
voidset(Object value)
Replaces the last element returned by next or previous with the specified element (optional operation).
voidsetReadModifyWrite(boolean lockForWrite)
Changes whether write-locks will be obtained when reading with this cursor.

Method Detail

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 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.

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.

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.

close

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

After being closed, only the StoredIterator and StoredIterator 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.

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. This method does not exist in the standard Iterator or ListIterator interfaces.

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().

dup

public final ListIterator dup()

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.

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.

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.

Returns: whether previous will succeed.

Throws: RuntimeExceptionWrapper if a DatabaseException is thrown.

isCurrentData

public final boolean isCurrentData(Object currentData)

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.

moveToIndex

public final boolean moveToIndex(int index)

next

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

Returns: the next 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.

Returns: the next index.

Throws: UnsupportedOperationException if this iterator's collection does not use record number keys. 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.

Returns: the previous element.

Throws: 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.

Returns: the previous index.

Throws: UnsupportedOperationException if this iterator's collection does not use record number keys. 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.

Throws: UnsupportedOperationException if the collection is a sublist, or if the collection is read-only. 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 interface.

Parameters: value the new value.

Throws: UnsupportedOperationException if the collection is a StoredKeySet (the set returned by java.util.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.

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.