com.spectralogic.ds3autogen.utils.collections.GuavaCollectors.java Source code

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/*
 * ******************************************************************************
 *   Copyright 2014-2015 Spectra Logic Corporation. All Rights Reserved.
 *   Licensed under the Apache License, Version 2.0 (the "License"). You may not use
 *   this file except in compliance with the License. A copy of the License is located at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 *   or in the "license" file accompanying this file.
 *   This file 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.
 * ****************************************************************************
 */

package com.spectralogic.ds3autogen.utils.collections;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;

import java.util.stream.Collector;

import static java.util.stream.Collector.Characteristics.UNORDERED;

/** Stream {@link Collector collectors} for Guava types. */
public final class GuavaCollectors {
    /** Collect a stream of elements into an {@link ImmutableList}. */
    public static <T> Collector<T, ImmutableList.Builder<T>, ImmutableList<T>> immutableList() {
        return Collector.of(ImmutableList.Builder::new, ImmutableList.Builder::add, (l, r) -> l.addAll(r.build()),
                ImmutableList.Builder<T>::build);
    }

    /** Collect a stream of elements into an {@link ImmutableSet}. */
    public static <T> Collector<T, ImmutableSet.Builder<T>, ImmutableSet<T>> immutableSet() {
        return Collector.of(ImmutableSet.Builder::new, ImmutableSet.Builder::add, (l, r) -> l.addAll(r.build()),
                ImmutableSet.Builder<T>::build, UNORDERED);
    }

    private GuavaCollectors() {
        throw new AssertionError("No instances.");
    }
}