org.apache.directory.shared.ldap.cursor
Class EmptyCursor<E>

java.lang.Object
  org.apache.directory.shared.ldap.cursor.AbstractCursor<E>
      org.apache.directory.shared.ldap.cursor.EmptyCursor<E>

All Implemented Interfaces:

java.lang.Iterable<E>, Cursor<E>

public class EmptyCursor<E>
extends AbstractCursor<E>

An empty Cursor implementation.

Version:

$Rev$, $Date$

Author:

Apache Directory Project

Constructor Summary

EmptyCursor()

Method Summary

void	after(E element) Prepares this Cursor, so a subsequent call to Cursor#previous() with a true return value, will have positioned the Cursor on a dataSet element equal to or less than the element argument but not greater.
void	afterLast() Positions this Cursor after the last element.
boolean	available() Determines whether or not a call to get() will succeed.
void	before(E element) Prepares this Cursor, so a subsequent call to Cursor#next() with a true return value, will have positioned the Cursor on a dataSet element equal to or less than the element argument but not greater.
void	beforeFirst() Positions this Cursor before the first element.
boolean	first() Positions this Cursor at the first element.
E	get() Gets the object at the current position.
boolean	isElementReused() Gets whether or not this Cursor will return the same element object instance on get() operations for any position of this Cursor.
boolean	last() Positions this Cursor at the last element.
boolean	next() Advances this Cursor to the next position.
boolean	previous() Advances this Cursor to the previous position.

Methods inherited from class org.apache.directory.shared.ldap.cursor.AbstractCursor

checkNotClosed, close, close, isClosed, iterator, setClosureMonitor

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

available

public boolean available()

Determines whether or not a call to get() will succeed.

Returns:

true if the cursor is valid get() will succeed, false otherwise

before

public void before(E element)
            throws java.lang.Exception

Prepares this Cursor, so a subsequent call to Cursor#next() with a true return value, will have positioned the Cursor on a dataSet element equal to or less than the element argument but not greater. A call to Cursor#previous() with a true return value will position the Cursor on a dataSet element less than the argument. If Cursor#next() returns false then the Cursor is past the last element and so all values in the dataSet are less than the argument. If Cursor#previous() returns false then the Cursor is positioned before the first element and all elements in the dataSet are greater than the argument.

Parameters:

element - the element to be positioned before

Throws:

java.lang.Exception - with problems accessing the underlying btree

java.lang.UnsupportedOperationException - if this method is not supported

after

public void after(E element)
           throws java.lang.Exception

Prepares this Cursor, so a subsequent call to Cursor#previous() with a true return value, will have positioned the Cursor on a dataSet element equal to or less than the element argument but not greater. A call to Cursor#next() with a true return value will position the Cursor on a dataSet element greater than the argument. If Cursor#next() returns false then the Cursor is past the last element and so all values in the dataSet are less than or equal to the argument. If Cursor#previous() returns false then the Cursor is positioned before the first element and all elements in the dataSet are greater than the argument.

Parameters:

element - the element to be positioned after

Throws:

java.lang.Exception - if there are problems positioning this cursor or if this Cursor is closed

java.lang.UnsupportedOperationException - if this method is not supported

beforeFirst

public void beforeFirst()
                 throws java.lang.Exception

Positions this Cursor before the first element.

Throws:

java.lang.Exception - if there are problems positioning this cursor or if this Cursor is closed

java.lang.UnsupportedOperationException - if this method is not supported

afterLast

public void afterLast()
               throws java.lang.Exception

Positions this Cursor after the last element.

Throws:

java.lang.Exception - if there are problems positioning this Cursor or if this Cursor is closed

java.lang.UnsupportedOperationException - if this method is not supported

first

public boolean first()
              throws java.lang.Exception

Positions this Cursor at the first element.

Returns:

true if the position has been successfully changed to the first element, false otherwise

Throws:

java.lang.Exception - if there are problems positioning this Cursor or if this Cursor is closed

java.lang.UnsupportedOperationException - if this method is not supported

last

public boolean last()
             throws java.lang.Exception

Positions this Cursor at the last element.

Returns:

true if the position has been successfully changed to the last element, false otherwise

Throws:

java.lang.Exception - if there are problems positioning this Cursor or if this Cursor is closed

java.lang.UnsupportedOperationException - if this method is not supported

previous

public boolean previous()
                 throws java.lang.Exception

Advances this Cursor to the previous position. If called before explicitly positioning this Cursor, the position is presumed to be after the last element and this method moves the cursor back to the last element.

Returns:

true if the advance succeeded, false otherwise

Throws:

java.lang.Exception - if there are problems advancing to the next position

java.lang.UnsupportedOperationException - if this method is not supported

next

public boolean next()
             throws java.lang.Exception

Advances this Cursor to the next position. If called before explicitly positioning this Cursor, the position is presumed to be before the first element and this method moves the cursor forward to the first element.

Returns:

true if the advance succeeded, false otherwise

Throws:

java.lang.Exception - if there are problems advancing to this Cursor to the next position, or if this Cursor is closed

java.lang.UnsupportedOperationException - if this method is not supported

get

public E get()
      throws java.lang.Exception

Gets the object at the current position. Cursor implementations may choose to reuse element objects by re-populating them on advances instead of creating new objects on each advance.

Returns:

the object at the current position

Throws:

java.lang.Exception - if the object at this Cursor's current position cannot be retrieved, or if this Cursor is closed

isElementReused

public boolean isElementReused()

Gets whether or not this Cursor will return the same element object instance on get() operations for any position of this Cursor. Some Cursor implementations may reuse the same element copying values into it for every position rather than creating and emit new element objects on each advance. Some Cursor implementations may return different elements for each position yet the same element instance is returned for the same position. In these cases this method should return true.

Returns:

true if elements are reused by this Cursor