it.unimi.di.mg4j.document
Class SubsetDocumentSequence

java.lang.Object
  it.unimi.di.mg4j.document.AbstractDocumentSequence
      it.unimi.di.mg4j.document.SubsetDocumentSequence

All Implemented Interfaces:

DocumentSequence, SafelyCloseable, Closeable, Serializable

public class SubsetDocumentSequence
extends AbstractDocumentSequence
implements Serializable

A collection that exhibits a subset of documents (possibly not contiguous) from a given sequence.

This class provides several string-based constructors that use the ObjectParser conventions; they can be used to generate easily subcollections from the command line.

Author:

Paolo Boldi

See Also:

Serialized Form

Constructor Summary

SubsetDocumentSequence(DocumentSequence underlyingSequence, IntSet documents)
Creates a new subsequence.

SubsetDocumentSequence(String underlyingSequenceBasename, String documentFileBasename)
Creates a new subsequence.

Method Summary

void	close() Closes this document sequence, releasing all resources.
DocumentFactory	factory() Returns the factory used by this sequence.
DocumentIterator	iterator() Returns an iterator over the sequence of documents.

Methods inherited from class it.unimi.di.mg4j.document.AbstractDocumentSequence

filename, finalize, load

Methods inherited from class java.lang.Object

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

Constructor Detail

SubsetDocumentSequence

public SubsetDocumentSequence(DocumentSequence underlyingSequence,
                              IntSet documents)

Creates a new subsequence.

Parameters:

underlyingSequence - the underlying document sequence.

documents - in the subsequence.

SubsetDocumentSequence

public SubsetDocumentSequence(String underlyingSequenceBasename,
                              String documentFileBasename)
                       throws NumberFormatException,
                              IllegalArgumentException,
                              SecurityException,
                              IOException,
                              ClassNotFoundException

Creates a new subsequence.

Parameters:

underlyingSequenceBasename - the basename of the underlying document sequence.

documentFileBasename - the basename of a file containing a serialized version of the set of document pointers to be retained.

Throws:

NumberFormatException

IllegalArgumentException

SecurityException

IOException

ClassNotFoundException

Method Detail

iterator

public DocumentIterator iterator()
                          throws IOException

Description copied from interface: DocumentSequence

Returns an iterator over the sequence of documents.

Warning: this method can be safely called just one time. For instance, implementations based on standard input will usually throw an exception if this method is called twice.

Implementations may decide to override this restriction (in particular, if they implement DocumentCollection). Usually, however, it is not possible to obtain two iterators at the same time on a collection.

Specified by:

iterator in interface DocumentSequence

Returns:

an iterator over the sequence of documents.

Throws:

IOException

See Also:

DocumentCollection

factory

public DocumentFactory factory()

Description copied from interface: DocumentSequence

Returns the factory used by this sequence.

Every document sequence is based on a document factory that transforms raw bytes into a sequence of characters. The factory contains useful information such as the number of fields.

Specified by:

factory in interface DocumentSequence

Returns:

the factory used by this sequence.

close

public void close()
           throws IOException

Description copied from interface: DocumentSequence

Closes this document sequence, releasing all resources.

You should always call this method after having finished with this document sequence. Implementations are invited to call this method in a finaliser as a safety net (even better, implement SafelyCloseable), but since there is no guarantee as to when finalisers are invoked, you should not depend on this behaviour.

Specified by:

close in interface DocumentSequence

Specified by:

close in interface Closeable

Overrides:

close in class AbstractDocumentSequence

Throws:

IOException