com.coyotegulch.jisp

Class BTreeIterator

java.lang.Object

com.coyotegulch.jisp.BTreeIterator

All Implemented Interfaces:

IndexIterator

public class BTreeIterator
extends java.lang.Object
implements IndexIterator

BTreeIterator defines an object that references a specific object relative to other objects in an ObjectIndex. In many ways, a BTreeIterator is analogous to the "cursors" found in SQL-type databases; it is essentially a movable reference to elements in an index, and it can be moved forward and backward through the list of keys.

See Also:

ObjectIndex, IndexedObjectDatabase

Constructor Summary

Constructors

Constructor and Description
BTreeIterator(BTreeIndex index) Creates a new BTreeIterator for a given index and database.
BTreeIterator(BTreeIterator iterator) Creates a new BTreeIterator that points to the same location as an existing BtreeIterator.

Method Summary

Modifier and Type	Method and Description
java.lang.Object	getKey() Returns the key Object currently associated with this iterator.
long	getRecPtr() Returns the reference (usually a file pointer) currently associated with this iterator.
void	invalidate() Sets this iterator's state to invalid.
boolean	isValid() Checks to see if this iterator is valid.
boolean	moveFirst() Moves this iterator to the first key and reference in sequence.
boolean	moveLast() Moves this iterator to the last key and reference in sequence.
boolean	moveNext() Moves this iterator to the next key and reference in sequence.
boolean	movePrevious() Moves this iterator to the previous key and reference in sequence.
boolean	moveTo(KeyObject key) Moves this iterator to point to the given key.
boolean	moveTo(KeyObject key, boolean acceptNext) Moves this iterator to point to the given key.

Methods inherited from class java.lang.Object

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

Constructor Detail

BTreeIterator

public BTreeIterator(BTreeIndex index)
              throws java.io.IOException,
                     java.lang.ClassNotFoundException

Creates a new BTreeIterator for a given index and database.

Parameters:

index - the index to which this iterator is attached.

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

See Also:

BTreeIndex

BTreeIterator

public BTreeIterator(BTreeIterator iterator)
              throws java.io.IOException,
                     java.lang.ClassNotFoundException

Creates a new BTreeIterator that points to the same location as an existing BtreeIterator.

Parameters:

iterator - the iterator to be copied.

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

See Also:

BTreeIndex

Method Detail

getRecPtr

public long getRecPtr()
               throws java.io.IOException

Returns the reference (usually a file pointer) currently associated with this iterator.

Specified by:

getRecPtr in interface IndexIterator

Returns:

the record Object currently referenced by this iterator, or -1 if the iterator is invalid

Throws:

java.io.IOException

getKey

public java.lang.Object getKey()
                        throws java.io.IOException

Returns the key Object currently associated with this iterator.

Specified by:

getKey in interface IndexIterator

Returns:

the key Object currently referenced by this iterator, or null if the iterator is invalid

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

moveNext

public boolean moveNext()
                 throws java.io.IOException,
                        java.lang.ClassNotFoundException

Moves this iterator to the next key and reference in sequence.

Specified by:

moveNext in interface IndexIterator

Returns:

true if the operation was successful; false otherwise.

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

movePrevious

public boolean movePrevious()
                     throws java.io.IOException,
                            java.lang.ClassNotFoundException

Moves this iterator to the previous key and reference in sequence.

Specified by:

movePrevious in interface IndexIterator

Returns:

true if the operation was successful; false otherwise.

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

BTreeException - when an error occurs during B-Tree processing

moveFirst

public boolean moveFirst()
                  throws java.io.IOException,
                         java.lang.ClassNotFoundException

Moves this iterator to the first key and reference in sequence.

Specified by:

moveFirst in interface IndexIterator

Returns:

true if the operation was successful; false otherwise.

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

BTreeException - when an error occurs during B-Tree processing

moveLast

public boolean moveLast()
                 throws java.io.IOException,
                        java.lang.ClassNotFoundException

Moves this iterator to the last key and reference in sequence.

Specified by:

moveLast in interface IndexIterator

Returns:

true if the operation was successful; false otherwise.

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

BTreeException - when an error occurs during B-Tree processing

moveTo

public boolean moveTo(KeyObject key)
               throws java.io.IOException,
                      java.lang.ClassNotFoundException

Moves this iterator to point to the given key.

Specified by:

moveTo in interface IndexIterator

Parameters:

key - key identifier to find

Returns:

true if the operation was successful; false otherwise.

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

BTreeException - when an error occurs during B-Tree processing

moveTo

public boolean moveTo(KeyObject key,
                      boolean acceptNext)
               throws java.io.IOException,
                      java.lang.ClassNotFoundException

Moves this iterator to point to the given key.

Specified by:

moveTo in interface IndexIterator

Parameters:

key - key identifier to find

acceptNext - when true, allows the search to return the next record in sequence if an exact match is not found

Returns:

true if the operation was successful; false otherwise.

Throws:

java.io.IOException - when an I/O exception is thrown by an underlying java.io.* class

java.lang.ClassNotFoundException - for a casting error, usually when a persistent object or index does match the expected type

BTreeException - when an error occurs during B-Tree processing

isValid

public boolean isValid()

Checks to see if this iterator is valid.

Specified by:

isValid in interface IndexIterator

Returns:

true if the iterator is valid; false if it is invalid.

invalidate

public void invalidate()

Sets this iterator's state to invalid.