DiqubeCollectors.java

/**
 * diqube: Distributed Query Base.
 *
 * Copyright (C) 2015 Bastian Gloeckle
 *
 * This file is part of diqube.
 *
 * diqube is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.diqube.util;

import java.util.NavigableSet;
import java.util.Set;
import java.util.TreeSet;
import java.util.function.Supplier;
import java.util.stream.Collector;
import java.util.stream.Collectors;

/**
 * Similar to {@link Collectors}, but with our custom functions.
 *
 * @author Bastian Gloeckle
 */
public class DiqubeCollectors {
  /**
   * Similar to {@link Collectors#toSet()}, but providing a {@link NavigableSet} instead of a normal {@link Set}.
   */
  public static <T> Collector<T, ?, NavigableSet<T>> toNavigableSet() {
    return Collector.of( //
        (Supplier<NavigableSet<T>>) TreeSet::new, //
        Set::add, //
        (left, right) -> {
          left.addAll(right);
          return left;
        } , //
        Collector.Characteristics.UNORDERED);
  }
}