org.apache.directory.shared.ldap.model.cursor
Interface Cursor<E>

Type Parameters:

E - The type of element on which this cursor will iterate

All Superinterfaces:

Iterable<E>

All Known Subinterfaces:

EntryCursor, SearchCursor, TupleCursor<K,V>

All Known Implementing Classes:

AbstractCursor, AbstractTupleCursor, EmptyCursor, ListCursor, SingletonCursor

public interface Cursor<E>
extends Iterable<E>

A Cursor for bidirectional traversal over elements in a dataSet. Cursors unlike Iterators or Enumerations may advance to an element by calling next() or previous() which returns true or false if the request succeeds with a viable element at the new position. Operations for relative positioning in larger increments are provided. If the cursor can not advance, then the Cursor is either positioned before the first element or after the last element in which case the user of the Cursor must stop advancing in the respective direction. If an advance succeeds a get() operation retrieves the current object at the Cursors position. Although this interface presumes Cursors can advance bidirectionally, implementations may restrict this by throwing UnsupportedOperationExceptions.

Author:

Apache Directory Project

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.
void	close() Closes this Cursor and frees any resources it my have allocated.
void	close(Exception reason) Closes this Cursor and frees any resources it my have allocated.
boolean	first() Positions this Cursor at the first element.
E	get() Gets the object at the current position.
boolean	isAfterLast() Is this Cursor positioned after the last element.
boolean	isBeforeFirst() Is this Cursor positioned before the first element.
boolean	isClosed() Checks if this Cursor is closed.
boolean	isFirst() Is this Cursor positioned at the first element.
boolean	isLast() Is this Cursor positioned at the last element.
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.
void	setClosureMonitor(ClosureMonitor monitor) Sets a non-null closure monitor to associate with this Cursor.

Methods inherited from interface java.lang.Iterable

iterator

Method Detail

available

boolean available()

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

Returns:

true if a call to the get() method will succeed, false otherwise

before

void before(E element)
            throws 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:

Exception - with problems accessing the underlying btree

after

void after(E element)
           throws 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:

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

beforeFirst

void beforeFirst()
                 throws Exception

Positions this Cursor before the first element.

Throws:

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

afterLast

void afterLast()
               throws Exception

Positions this Cursor after the last element.

Throws:

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

first

boolean first()
              throws Exception

Positions this Cursor at the first element.

Returns:

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

Throws:

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

isFirst

boolean isFirst()
                throws Exception

Is this Cursor positioned at the first element.

Returns:

true if this cursor is positioned at the first element, false otherwise

Throws:

Exception - if there are problems querying the position of this Cursor or if this Cursor is closed

isBeforeFirst

boolean isBeforeFirst()
                      throws Exception

Is this Cursor positioned before the first element.

Returns:

true if this cursor is positioned before the first element, false otherwise

Throws:

Exception - if there are problems querying the position of this Cursor or if this Cursor is closed

last

boolean last()
             throws Exception

Positions this Cursor at the last element.

Returns:

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

Throws:

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

isLast

boolean isLast()
               throws Exception

Is this Cursor positioned at the last element.

Returns:

true if this cursor is positioned at the last element, false otherwise

Throws:

Exception - if there are problems querying the position of this Cursor or if this Cursor is closed

isAfterLast

boolean isAfterLast()
                    throws Exception

Is this Cursor positioned after the last element.

Returns:

true if this cursor is positioned after the last element, false otherwise

Throws:

Exception - if there are problems querying the position of this Cursor or if this Cursor is closed

isClosed

boolean isClosed()
                 throws Exception

Checks if this Cursor is closed. Calls to this operation should not fail with exceptions if and only if the cursor is in the closed state.

Returns:

true if this Cursor is closed, false otherwise

Throws:

Exception - if there are problems determining the cursor's closed state

previous

boolean previous()
                 throws 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:

Exception - if there are problems advancing to the next position

next

boolean next()
             throws 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:

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

get

E get()
      throws 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:

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

close

void close()
           throws Exception

Closes this Cursor and frees any resources it my have allocated. Repeated calls to this method after this Cursor has already been called should not fail with exceptions.

Throws:

Exception - if for some reason this Cursor could not be closed

close

void close(Exception reason)
           throws Exception

Closes this Cursor and frees any resources it my have allocated. Repeated calls to this method after this Cursor has already been called should not fail with exceptions. The reason argument is the Exception instance thrown instead of the standard CursorClosedException.

Parameters:

reason - exception thrown when this Cursor is accessed after close

Throws:

Exception - if for some reason this Cursor could not be closed

setClosureMonitor

void setClosureMonitor(ClosureMonitor monitor)

Sets a non-null closure monitor to associate with this Cursor.

Parameters:

monitor - the monitor to use for detecting Cursor close events