xxl.cursors
Class Grouper

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

public class Grouper

extends java.lang.Object

implements Cursor

A Grouper partitions input data into groups (lazy evaluation). A binary Function is used to compare the actual with the last element. If the Function returns true a new group starts. A call to next() returns a Cursor pointing to the next group.

Field Summary

protected Cursor	cursor The Cursor to be wrapped.
protected Function	function The Function used to compare two elements.
protected int	groupSize The actual size of the group.
protected boolean	hasPeeked
protected java.lang.Object	prePrevious The Object seen before the actual Object.
protected java.lang.Object	previous The Object seen before the actual Object.
protected boolean	updatePossible

Constructor Summary

Grouper(Cursor cursor, Function function)
Creates a new Grouper.

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

Grouper(PeekIterator peekIterator, Function function)
Creates a new Grouper.

Method Summary

void	close() Closes the Cursor.
boolean	hasNext() Returns true if the iteration has more elements.
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 (Always returns false).
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

The Cursor to be wrapped.

function

protected Function function

The Function used to compare two elements.

previous

protected java.lang.Object previous

The Object seen before the actual Object.

prePrevious

protected java.lang.Object prePrevious

The Object seen before the actual Object.

groupSize

protected int groupSize

The actual size of the group.

hasPeeked

protected boolean hasPeeked

updatePossible

protected boolean updatePossible

Constructor Detail

Grouper

public Grouper(Cursor cursor,
               Function function)

Creates a new Grouper.

Parameters:

cursor - the Cursor to be wrapped

function - the Function used to compare two elements

Grouper

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

Creates a new Grouper.

Parameters:

iterator - the iterator to be wrapped

function - the Function used to compare two elements

Grouper

public Grouper(PeekIterator peekIterator,
               Function function)

Creates a new Grouper.

Parameters:

peekIterator - the PeekIterator to be wrapped

function - the Function used to compare two elements

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.

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.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 (Always returns false).

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 foow 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()