src.it.unimi.dsi.util.StringMap Maven / Gradle / Ivy
/*
* DSI utilities
*
* Copyright (C) 2008-2023 Sebastiano Vigna
*
* This program and the accompanying materials are made available under the
* terms of the GNU Lesser General Public License v2.1 or later,
* which is available at
* http://www.gnu.org/licenses/old-licenses/lgpl-2.1-standalone.html,
* or the Apache Software License 2.0, which is available at
* https://www.apache.org/licenses/LICENSE-2.0.
*
* 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.
*
* SPDX-License-Identifier: LGPL-2.1-or-later OR Apache-2.0
*/
package it.unimi.dsi.util;
import java.io.Serializable;
import it.unimi.dsi.fastutil.objects.Object2LongFunction;
import it.unimi.dsi.fastutil.objects.ObjectList;
/** A map from strings to numbers (and possibly vice versa).
*
* String maps represent mappings from strings (actually, any subclass of {@link CharSequence})
* to numbers; they can support {@linkplain #list() reverse
* mapping}, too. The latter has usually sense only if the map is minimal and perfect (e.g., a bijection of a set
* of string with an initial segment of the natural numbers of the same size). String maps are useful for
* terms of an MG4J
* inverted index, URLs of a WebGraph-compressed
* web snapshot, and so on.
*
*
Warning: the return value of {@link #list()} is a fastutil {@link ObjectList}.
* This in principle is not sensible, as string maps return longs (they extend
* {@link Object2LongFunction}), and {@link ObjectList} has only integer index
* support. If you need long indices, please consider using {@link it.unimi.dsi.big.util.StringMap}.
*
* @author Sebastiano Vigna
* @since 0.2
*/
public interface StringMap extends Object2LongFunction, Serializable {
/** Returns a list view of the domain of this string map (optional operation).
*
* Note that the list view acts as an inverse of the mapping implemented by this map.
*
* @return a list view of the domain of this string map, or {@code null} if this map does
* not support this operation.
*/
ObjectList list();
}