org.grouplens.lenskit.cursors

Class AbstractCursor<T>

java.lang.Object

org.grouplens.lenskit.cursors.AbstractCursor<T>

Type Parameters:

T - The type of value returned by this cursor.

All Implemented Interfaces:

Closeable, AutoCloseable, Iterable<T>, Cursor<T>

Direct Known Subclasses:

AbstractPollingCursor, DelimitedTextCursor, GroupingCursor

public abstract class AbstractCursor<T>
extends Object
implements Cursor<T>

Base class to make Cursors easier to implement.

Compatibility

Public

Constructor Summary

Constructors

Constructor and Description
AbstractCursor() Construct a cursor of unknown size.
AbstractCursor(int nrows) Construct a cursor.

Method Summary

Modifier and Type	Method and Description
void	close() No-op implementation of the Cursor.close() method.
Iterable<T>	fast() Deprecated.
T	fastNext() Deprecated.
int	getRowCount() Get an upper bound on the number of rows available from the cursor.
Iterator<T>	iterator() Get the iterator.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.grouplens.lenskit.cursors.Cursor

hasNext, next

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Detail

AbstractCursor

public AbstractCursor()

Construct a cursor of unknown size.

AbstractCursor

public AbstractCursor(int nrows)

Construct a cursor.

Parameters:

nrows - The number of rows, or -1 for unknown size.

Method Detail

getRowCount

public int getRowCount()

Description copied from interface: Cursor

Get an upper bound on the number of rows available from the cursor.

Specified by:

getRowCount in interface Cursor<T>

Returns:

the maximum number of rows which may be returned by Cursor.next(), or -1 if that count is not available.

close

public void close()

No-op implementation of the Cursor.close() method.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Cursor<T>

fastNext

@Nonnull
 @Deprecated
public T fastNext()

Deprecated.

Variant of Cursor.next() that may mutate and return the same object avoid excess allocations. Since many loops don't do anything with the object after the iteration in which it is retrieved, using this iteration method can improve both speed and memory use.

This implementation delegates to Cursor.next().

Specified by:

fastNext in interface Cursor<T>

Returns:

The next element from the cursor, reusing objects if possible.

See Also:

Cursor.next()

fast

@Deprecated
public Iterable<T> fast()

Deprecated.

Description copied from interface: Cursor

Convert the cursor to an iterable whose Iterator.next() method is implemented in terms of Cursor.fastNext().

Specified by:

fast in interface Cursor<T>

Returns:

An iterable for fast iteration.

iterator

public Iterator<T> iterator()

Get the iterator. This method just returns this, so for-each loops can be used over cursors.

Specified by:

iterator in interface Iterable<T>

Returns:

The cursor as an iterator.

See Also:

Iterable.iterator()