uk.co.lucasweb.stream.ImmutableSetCollector.java Source code

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Here is the source code for uk.co.lucasweb.stream.ImmutableSetCollector.java

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/*
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 *   the License. You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 *   an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 *   specific language governing permissions and limitations under the License.
 *
 *   Copyright 2016 the original author or authors.
 *
 */

package uk.co.lucasweb.stream;

import com.google.common.collect.ImmutableSet;

import java.util.EnumSet;
import java.util.Set;
import java.util.function.BiConsumer;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collector;

/**
 * Custom {@link Collector} that accumulates the input elements into a Guava {@link ImmutableSet}.
 *
 * @param <E>
 *         the type of elements in the set
 * @author Richard Lucas
 */
public class ImmutableSetCollector<E> implements Collector<E, ImmutableSet.Builder<E>, ImmutableSet<E>> {

    public static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
        return new ImmutableSetCollector<>();
    }

    @Override
    public Supplier<ImmutableSet.Builder<E>> supplier() {
        return ImmutableSet::builder;
    }

    @Override
    public BiConsumer<ImmutableSet.Builder<E>, E> accumulator() {
        return ImmutableSet.Builder::add;
    }

    @Override
    public BinaryOperator<ImmutableSet.Builder<E>> combiner() {
        return (left, right) -> {
            left.addAll(right.build());
            return left;
        };
    }

    @Override
    public Function<ImmutableSet.Builder<E>, ImmutableSet<E>> finisher() {
        return ImmutableSet.Builder::build;
    }

    @Override
    public Set<Characteristics> characteristics() {
        return EnumSet.of(Characteristics.UNORDERED);
    }

}