xxl.cursors
Class Aggregator

java.lang.Object
  |
  +--xxl.cursors.Aggregator

Direct Known Subclasses:

Minimator

public class Aggregator

extends java.lang.Object

implements Cursor

The Aggregator computes an aggregate for an input-Iterator.

Field Summary

protected java.lang.Object	aggregate
protected Cursor	cursor Input-Cursor.
protected Function	function
protected boolean	initialized

Constructor Summary

Aggregator(Cursor cursor, Function function, java.lang.Object aggregate)
Creates a new Aggregator.

Aggregator(java.util.Iterator iterator, Function function)
Creates a new Aggregator.

Aggregator(java.util.Iterator iterator, Function function, java.lang.Object aggregate)
Creates a new Aggregator.

Aggregator(PeekIterator peekIterator, Function function, java.lang.Object aggregate)
Creates a new Aggregator.

Method Summary

void	close() Closes the Cursor.
boolean	hasNext() Returns true if the iteration has more elements.
java.lang.Object	last() Returns the last element of this Cursor.
java.lang.Object	next() Returns the next element in the iteration.
java.lang.Object	peek() Shows the next element in the iteration without removing it.
void	remove() Removes from the underlying collection the last element returned by the iterator (optional operation).
void	reset() Resets the Cursor to its initial state.
boolean	supportsPeek() Returns true if the peek operation is supported by this PeekIterator.
void	update(java.lang.Object object) Replaces the object that was returned by the last call to next() or peek().

Methods inherited from class java.lang.Object

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

Field Detail

cursor

protected Cursor cursor

Input-Cursor.

function

protected Function function

aggregate

protected java.lang.Object aggregate

initialized

protected boolean initialized

Constructor Detail

Aggregator

public Aggregator(Cursor cursor,
                  Function function,
                  java.lang.Object aggregate)

Creates a new Aggregator.

Parameters:

cursor - input-Cursor

function - used for the aggregation

aggregate - result-object for the aggregation

Aggregator

public Aggregator(java.util.Iterator iterator,
                  Function function,
                  java.lang.Object aggregate)

Creates a new Aggregator.

Parameters:

iterator - input-Iterator

function - used for the aggregation

aggregate - result-object for the aggregation

Aggregator

public Aggregator(PeekIterator peekIterator,
                  Function function,
                  java.lang.Object aggregate)

Creates a new Aggregator.

Parameters:

peekIterator - input-PeekIterator

function - used for the aggregation

aggregate - result-object for the aggregation

Aggregator

public Aggregator(java.util.Iterator iterator,
                  Function function)

Creates a new Aggregator.

Parameters:

iterator - input-Iterator

function - used for the aggregation

Method Detail

close

public void close()

Closes the Cursor. Signals the cursor to cleanup resources, close files, etc. After a call to close() calls to methods like next() or peek() are not guarantied to yield proper results. ‰

Specified by:

close in interface Cursor

hasNext

public boolean hasNext()

Returns true if the iteration has more elements.

Specified by:

hasNext in interface Cursor

Returns:

true if the iterator has more elements.

last

public java.lang.Object last()
                      throws java.util.NoSuchElementException

Returns the last element of this Cursor.

next

public java.lang.Object next()
                      throws java.util.NoSuchElementException

Returns the next element in the iteration.

Specified by:

next in interface Cursor

Returns:

the next element in the iteration.

Throws:

java.util.NoSuchElementException - iteration has no more elements.

peek

public java.lang.Object peek()
                      throws java.util.NoSuchElementException,
                             java.lang.UnsupportedOperationException

Shows the next element in the iteration without removing it.

Specified by:

peek in interface Cursor

Returns:

the next element in the iteration.

Throws:

java.util.NoSuchElementException - iteration has no more elements.

java.lang.UnsupportedOperationException - if the peek operation is not supported by this PeekIterator.

remove

public void remove()
            throws java.lang.UnsupportedOperationException

Removes from the underlying collection the last element returned by the iterator (optional operation).

Specified by:

remove in interface Cursor

Throws:

java.lang.IllegalStateException - if the next method has not yet been called, or the remove method has already been called after the last call to the next method.

java.lang.UnsupportedOperationException - if the remove operation is not supported by this PeekIterator.

reset

public void reset()
           throws java.lang.UnsupportedOperationException

Resets the Cursor to its initial state.

Specified by:

reset in interface Cursor

supportsPeek

public boolean supportsPeek()

Returns true if the peek operation is supported by this PeekIterator.

Specified by:

supportsPeek in interface Cursor

Returns:

true if the peek operation is supported by this PeekIterator.

update

public void update(java.lang.Object object)
            throws java.lang.UnsupportedOperationException

Replaces the object that was returned by the last call to next() or peek(). This operation must not be called after a call to hasNext(). It should follow a call to next() or peek().

Specified by:

update in interface Cursor

Parameters:

object - the object that replaces the object returned by the last call to next() or peek()