Package org.opends.server.backends.pluggable.spi

Class EmptyCursor<K,V>

java.lang.Object

org.opends.server.backends.pluggable.spi.EmptyCursor<K,V>

Type Parameters:

K - Type of the simulated record's key

V - Type of the simulated record's value

All Implemented Interfaces:

Closeable, AutoCloseable, Cursor<K,V>, SequentialCursor<K,V>

public final class EmptyCursor<K,V>
extends Object
implements Cursor<K,V>

Implementation of an empty Cursor, for simulating no records to cursor on.

Cursor behaves as follows:

• Positioning to a key or index will fail, returning false.
• Reading the key or value will return null.
• Deleting the current element is not supported, UnsupportedOperationException will be thrown.

Constructor Summary

Constructors

Constructor	Description
EmptyCursor()

Method Summary

Modifier and Type	Method	Description
void	close()
void	delete()	Deletes the record on which this cursor is currently positioned.
K	getKey()	Returns the key of the record on which this cursor is currently positioned.
V	getValue()	Returns the value of the record on which this cursor is currently positioned.
boolean	isDefined()	Check whether this cursor is currently pointing to valid record.
boolean	next()	Moves this cursor to the next record in the tree.
boolean	positionToIndex(int index)	Positions the cursor to the specified index within the tree.
boolean	positionToKey(ByteSequence key)	Positions the cursor to the provided key if it exists in the tree.
boolean	positionToKeyOrNext(ByteSequence key)	Positions the cursor to the provided key if it exists in the tree, or else the lesser key greater than the provided key in the tree.
boolean	positionToLastKey()	Positions the cursor to the last key in the tree.

Methods inherited from class java.lang.Object

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

Constructor Detail

EmptyCursor

public EmptyCursor()

Method Detail

positionToKey

public boolean positionToKey(ByteSequence key)

Description copied from interface: Cursor

Positions the cursor to the provided key if it exists in the tree.

Specified by:

positionToKey in interface Cursor<K,V>

Parameters:

key - the key where to position the cursor

Returns:

true if the cursor could be positioned to the key, false otherwise

positionToKeyOrNext

public boolean positionToKeyOrNext(ByteSequence key)

Description copied from interface: Cursor

Positions the cursor to the provided key if it exists in the tree, or else the lesser key greater than the provided key in the tree.

Specified by:

positionToKeyOrNext in interface Cursor<K,V>

Parameters:

key - the key where to position the cursor

Returns:

true if the cursor could be positioned to the key or the next one, false otherwise

positionToLastKey

public boolean positionToLastKey()

Description copied from interface: Cursor

Positions the cursor to the last key in the tree.

Specified by:

positionToLastKey in interface Cursor<K,V>

Returns:

true if the cursor could be positioned to the last key, false otherwise

positionToIndex

public boolean positionToIndex(int index)

Description copied from interface: Cursor

Positions the cursor to the specified index within the tree. Implementations may take advantage of optimizations provided by the underlying storage, such as counted B-Trees.

Specified by:

positionToIndex in interface Cursor<K,V>

Parameters:

index - the index where the cursor should be positioned, (0 is the first record).

Returns:

true if the cursor could be positioned to the index, false otherwise

next

public boolean next()

Description copied from interface: SequentialCursor

Moves this cursor to the next record in the tree.

Specified by:

next in interface SequentialCursor<K,V>

Returns:

true if the cursor has moved to the next record, false if no next record exists leaving cursor in undefined state.

isDefined

public boolean isDefined()

Description copied from interface: SequentialCursor

Check whether this cursor is currently pointing to valid record.

Specified by:

isDefined in interface SequentialCursor<K,V>

Returns:

true if the cursor is pointing to a valid entry, false if cursor is not pointing to a valid entry

getKey

public K getKey()
         throws NoSuchElementException

Description copied from interface: SequentialCursor

Returns the key of the record on which this cursor is currently positioned.

Specified by:

getKey in interface SequentialCursor<K,V>

Returns:

the current record's key.

Throws:

NoSuchElementException - if the cursor is not defined.

getValue

public V getValue()
           throws NoSuchElementException

Description copied from interface: SequentialCursor

Returns the value of the record on which this cursor is currently positioned.

Specified by:

getValue in interface SequentialCursor<K,V>

Returns:

the current record's value.

Throws:

NoSuchElementException - if the cursor is not defined.

delete

public void delete()
            throws NoSuchElementException,
                   UnsupportedOperationException

Description copied from interface: SequentialCursor

Deletes the record on which this cursor is currently positioned. This method does not alter the position of the cursor. In particular, SequentialCursor.next() must be called in order to point to the next record. The behavior of methods SequentialCursor.getKey() and SequentialCursor.getValue() after this method returns is undefined.

Specified by:

delete in interface SequentialCursor<K,V>

Throws:

NoSuchElementException - if the cursor is not defined.

UnsupportedOperationException - if the cursor implementation does not support updates.

close

public void close()

Description copied from interface: SequentialCursor

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface SequentialCursor<K,V>