com.wrmsr.neurosis.util.ImmutableCollectors.java Source code

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Here is the source code for com.wrmsr.neurosis.util.ImmutableCollectors.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.
 */
package com.wrmsr.neurosis.util;

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

import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collector;

public final class ImmutableCollectors {
    private ImmutableCollectors() {
    }

    public static <T> Collector<T, ?, ImmutableList<T>> toImmutableList() {
        return Collector.<T, ImmutableList.Builder<T>, ImmutableList<T>>of(ImmutableList.Builder::new,
                ImmutableList.Builder::add, (left, right) -> {
                    left.addAll(right.build());
                    return left;
                }, ImmutableList.Builder::build);
    }

    public static <T> Collector<T, ?, ImmutableSet<T>> toImmutableSet() {
        return Collector.<T, ImmutableSet.Builder<T>, ImmutableSet<T>>of(ImmutableSet.Builder::new,
                ImmutableSet.Builder::add, (left, right) -> {
                    left.addAll(right.build());
                    return left;
                }, ImmutableSet.Builder::build, Collector.Characteristics.UNORDERED);
    }

    public static <T> Collector<T, ?, ImmutableMultiset<T>> toImmutableMultiset() {
        return Collector.<T, ImmutableMultiset.Builder<T>, ImmutableMultiset<T>>of(ImmutableMultiset.Builder::new,
                ImmutableMultiset.Builder::add, (left, right) -> {
                    left.addAll(right.build());
                    return left;
                }, ImmutableMultiset.Builder::build, Collector.Characteristics.UNORDERED);
    }

    public static <I, K, V> Collector<I, ImmutableMap.Builder<K, V>, ImmutableMap<K, V>> toImmutableMap(
            Function<I, K> keyMapper, Function<I, V> valueMapper) {
        return Collector.of(ImmutableMap::builder,
                (builder, in) -> builder.put(keyMapper.apply(in), valueMapper.apply(in)),
                (ImmutableMap.Builder<K, V> left, ImmutableMap.Builder<K, V> right) -> left.putAll(right.build()),
                ImmutableMap.Builder<K, V>::build);
    }

    public static <K, V> Collector<Map.Entry<K, V>, ImmutableMap.Builder<K, V>, ImmutableMap<K, V>> toImmutableMap() {
        return toImmutableMap(Map.Entry::getKey, Map.Entry::getValue);
    }
}