org.lenskit.api.Result Maven / Gradle / Ivy
/*
* LensKit, an open source recommender systems toolkit.
* Copyright 2010-2014 LensKit Contributors. See CONTRIBUTORS.md.
* Work on LensKit has been funded by the National Science Foundation under
* grants IIS 05-34939, 08-08692, 08-12148, and 10-17697.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 51
* Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
package org.lenskit.api;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
/**
* A LensKit result, consisting of a score and an ID. Individual recommenders may subclass this component to provide
* more detailed results.
*
* Implementations must create well-defined equality. However, instances of different implementations are not required
* or expected to be able to be equal to each other. Instances are not allowed to be equal if they have different IDs.
*/
public interface Result {
/**
* Get the ID for the result.
* @return The user or item ID for this result.
*/
long getId();
/**
* Get the score (value) associated with this result.
* @return The score associated with this entry (or {@link Double#NaN} if the result does not have a score).
*/
double getScore();
/**
* Query whether the result has a score. This is equivalent to testing the return value of {@link #getScore()} with
* {@link Double#isNaN(double)}, but may make the resulting code more readable.
*
* @return `true` if the result has a score.
*/
boolean hasScore();
/**
* Convert this result to the specified type, if possible.
*
* @param type The desired result type.
* @param The desired result type.
* @return The result as a result of type `T`, or `null` if the type cannot be cast. This may be done by casting
* this type, or by unwrapping wrapper result types.
*/
@Nullable
T as(@Nonnull Class type);
}