DefaultValueProvider.java

/*
 *      Copyright (C) 2012, 2016  higherfrequencytrading.com
 *      Copyright (C) 2016 Roman Leventov
 *
 *      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 3 of the License.
 *
 *      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 Lesser General Public License for more details.
 *
 *      You should have received a copy of the GNU Lesser General Public License
 *      along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.openhft.chronicle.map;

import net.openhft.chronicle.hash.Data;
import org.jetbrains.annotations.NotNull;

/**
 * Default value computation strategy, used
 * in {@link ChronicleMapBuilder#defaultValueProvider(DefaultValueProvider)} configuration.
 *
 * @param <K> map key class
 * @param <V> map value class
 */
@FunctionalInterface
public interface DefaultValueProvider<K, V> {

    /**
     * Returns the "nil" value, which should be inserted into the map, in the given
     * {@code absentEntry} context. This is primarily used in {@link ChronicleMap#acquireUsing}
     * operation implementation, i. e. {@link MapMethods#acquireUsing}.
     *
     * The default implementation simply delegates to {@link MapAbsentEntry#defaultValue()}.
     */
    Data<V> defaultValue(@NotNull MapAbsentEntry<K, V> absentEntry);
}