xxl.cursors
Class HashGrouper

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

public class HashGrouper

extends java.lang.Object

implements Cursor

A HashGrouper partitions input data into groups (strict evaluation). A HashGrouper calls next() on the input-Cursor until hasNext() returns false. This means that the HashGrouper partitions the data physically. 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
protected Function	function The Function used to compare two elements.
protected Cursor	groups A Cursor pointing to the resulting groups.

Constructor Summary

HashGrouper(Cursor cursor, Function function)
Creates a HashGrouper.

HashGrouper(java.util.Iterator iterator)
Creates a HashGrouper.

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

HashGrouper(PeekIterator peekIterator, Function function)
Creates a HashGrouper.

Method Summary

void	close() Closes the Cursor.
boolean	hasNext() Returns true if the iteration has more elements.
protected void	init() Initializes the HashGrouper.
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

groups

protected Cursor groups

A Cursor pointing to the resulting groups.

cursor

protected Cursor cursor

function

protected Function function

The Function used to compare two elements.

Constructor Detail

HashGrouper

public HashGrouper(Cursor cursor,
                   Function function)

Creates a HashGrouper.

Parameters:

cursor - the Cursor to be wrapped

function - the Function used to compare two elements

HashGrouper

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

Creates a HashGrouper.

Parameters:

iterator - the Iterator to be wrapped

function - the Function used to compare two elements

HashGrouper

public HashGrouper(PeekIterator peekIterator,
                   Function function)

Creates a HashGrouper.

Parameters:

peekIterator - the PeekIterator to be wrapped

function - the Function used to compare two elements

HashGrouper

public HashGrouper(java.util.Iterator iterator)

Creates a HashGrouper.

Parameters:

iterator - the Iterator to be wrapped

Method Detail

init

protected void init()

Initializes the HashGrouper. Partitions the input data.

close

public void close()
           throws java.util.NoSuchElementException

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()