com.davisor.data.stream
Class IteratorDataStream

java.lang.Object
  com.davisor.data.VoidData
      com.davisor.data.stream.IteratorDataStream

All Implemented Interfaces:

Data, DataStream

Direct Known Subclasses:

IteratorTypeStream, ListIteratorDataStream, PivotDataStream, SortDataStream

public class IteratorDataStream

extends VoidData

implements DataStream

IteratorDataStream represents a data stream that uses a standard Java iterator to implement stream elements. The elements may or may not be DataValues, and they may or may not be of a mutually equal type. The stream itself has a single type, however.

References to DataValue elements are returned as they are. Elements not of the expected type are converted first to data objects of the proper type, and then the converted objects are returned. The original objects in the source are not changed.

Since:

JDK1.1

See Also:

next(), EnumeratorDataStream, Type

Field Summary

protected boolean	M_hasNext Is there still data in this stream.
protected long	M_index Element id counter.
protected java.util.Iterator	M_iterator Underlying stream iterator.
protected java.lang.Object	M_metaData Stream meta data (may be null).
protected DataValue	M_nextData Reference to the next data element to be returned (may be null).

Fields inherited from class com.davisor.data.VoidData

M_type

Fields inherited from interface com.davisor.data.stream.DataStream

INITIAL_INDEX

Constructor Summary

	IteratorDataStream(java.util.Collection collection) Creates a data stream out of a collection.
	IteratorDataStream(java.util.Collection collection, Type type) Creates a data stream out of a collection and given type.
	IteratorDataStream(java.util.Iterator iterator) Creates a data stream out of an iterator.
	IteratorDataStream(java.util.Iterator iterator, Type type) Creates a data stream out of an iterator and the given type.
protected	IteratorDataStream(Type type) Creates a new data stream out of a given type.

Method Summary

boolean	close() Explicitly closes this data stream, and frees all system resources it has allocated immediately.
long	getIndex() Retrieves the index number of the element returned by the latest next() call.
boolean	hasNext() Tests if the stream still contains data.
protected void	init(java.util.Iterator iterator) Initializes this iterator stream with given iterator.
DataValue	next() Gets the next data value from the stream.
java.lang.String	toString() Gets the string representation of this data stream.

Methods inherited from class com.davisor.data.VoidData

equals, getDataValue, getType, hashCode, setType

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface com.davisor.data.Data

getType

Field Detail

M_nextData

protected DataValue M_nextData

Reference to the next data element to be returned (may be null).

M_index

protected long M_index

Element id counter.

M_iterator

protected java.util.Iterator M_iterator

Underlying stream iterator.

M_hasNext

protected boolean M_hasNext

Is there still data in this stream.

M_metaData

protected java.lang.Object M_metaData

Stream meta data (may be null).

Constructor Detail

IteratorDataStream

protected IteratorDataStream(Type type)

Creates a new data stream out of a given type. This is a protected constructor for special sub-clases that wish to leave the the stream iterator and next object initially uninitialized.

Parameters:

type - the type of data in stream

See Also:

VoidData.getType(), init(java.util.Iterator)

IteratorDataStream

public IteratorDataStream(java.util.Collection collection)
                   throws InvalidDataException

Creates a data stream out of a collection. The data stream type is taken from the first element in the collection.

Parameters:

collection - data collection to create a stream from

Throws:

InvalidDataException - if the first element is not a DataValue

See Also:

IteratorDataStream(Collection,Type)

IteratorDataStream

public IteratorDataStream(java.util.Collection collection,
                          Type type)
                   throws InvalidDataException

Creates a data stream out of a collection and given type.

Parameters:

collection - data collection to create a stream from

type - the type of data in stream

Throws:

InvalidDataException - if the first element is not of the given type, and cannot be converted to a data object of that type

See Also:

IteratorDataStream(Iterator,Type)

IteratorDataStream

public IteratorDataStream(java.util.Iterator iterator)
                   throws InvalidDataException

Creates a data stream out of an iterator. The data stream type is set to AutoType.

Parameters:

iterator - data iterator to create a stream from

Throws:

InvalidDataException - if the first element was not a DataValue, and no suitable type could be created for it

See Also:

IteratorDataStream(Iterator,Type), AutoType

IteratorDataStream

public IteratorDataStream(java.util.Iterator iterator,
                          Type type)
                   throws InvalidDataException

Creates a data stream out of an iterator and the given type. Returns nulls as they are (i.e. nulls).

Parameters:

iterator - data iterator to create a stream from

type - the type of data in stream

Throws:

InvalidDataException - if the first element is not of the given type, and cannot be converted to a data object of that type.

See Also:

IteratorDataStream(Collection,Type), IteratorDataStream(Iterator), init(java.util.Iterator)

Method Detail

close

public boolean close()

Explicitly closes this data stream, and frees all system resources it has allocated immediately. For iterator steams, the reference to underlying iterator object is dropped, which makes the iterator object subject to garbage collection, at least as far this data stream is concerned.

Specified by:

close in interface DataStream

Returns:

always true

See Also:

init(java.util.Iterator)

getIndex

public long getIndex()

Retrieves the index number of the element returned by the latest next() call. The index represents the position of the element within this stream. The stream index may or may not be equal to any other indexes the element itself thinks it posesses.

The index value is initially INITIAL_INDEX (-1), indicating no element. After first next() call, index becomes 0, then 1, and so on. This functionality resembles java.sql.resultSet#getRow method functionality, but with the difference that the index counter starts from 0, not 1.

Specified by:

getIndex in interface DataStream

Returns:

element index

hasNext

public boolean hasNext()

Tests if the stream still contains data.

Specified by:

hasNext in interface DataStream

Returns:

true if it does.

next

public DataValue next()
               throws InvalidDataException

Gets the next data value from the stream. Null values coming from the stream are not converted to DataValues, but they are returned as nulls.

Specified by:

next in interface DataStream

Throws:

InvalidDataException - if the stream content does not satisfy the stream type

See Also:

close(), VoidData.getDataValue(java.lang.Object), hasNext(), init(java.util.Iterator)

toString

public java.lang.String toString()

Gets the string representation of this data stream. This however consumes the stream entirely, taking the current iterator from it's current position to the end of the stream.

Overrides:

toString in class VoidData

See Also:

hasNext(), next()

init

protected void init(java.util.Iterator iterator)
             throws InvalidDataException

Initializes this iterator stream with given iterator. In particular, the given iterator hasNext() status is inspected at this time. If the iterator is not null and it has a next element, stream hasNext() status is set to true, and the next iterator element is set to be the next() stream object to be returned. Otherwise stream hasNext() status is set to false, and the next iterator element is set to null.

The stream index is also set to INITIAL_INDEX (-1) value.

Parameters:

iterator - the iterator to initialize this stream with (may be null)

Throws:

InvalidDataException - if the first element is not a DataValue

See Also:

VoidData.getDataValue(java.lang.Object)