org.javimmutable.collections.util.JImmutableCollectors Maven / Gradle / Ivy

Go to download
///###////////////////////////////////////////////////////////////////////////
//
// Burton Computer Corporation
// http://www.burton-computer.com
//
// Copyright (c) 2017, Burton Computer Corporation
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//     Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
//
//     Redistributions in binary form must reproduce the above copyright
//     notice, this list of conditions and the following disclaimer in
//     the documentation and/or other materials provided with the
//     distribution.
//
//     Neither the name of the Burton Computer Corporation nor the names
//     of its contributors may be used to endorse or promote products
//     derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package org.javimmutable.collections.util;

import org.javimmutable.collections.Func2;
import org.javimmutable.collections.JImmutableList;
import org.javimmutable.collections.JImmutableListMap;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.JImmutableRandomAccessList;
import org.javimmutable.collections.JImmutableSet;

import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;
import java.util.Comparator;
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;
import java.util.stream.Collector.Characteristics;

/**
 * Utility class providing static methods for collecting various immutable collections using streams.
 */
public class JImmutableCollectors
{
    static final Set ORDERED = JImmutables.set(Characteristics.CONCURRENT).getSet();
    static final Set UNORDERED = JImmutables.set(Characteristics.UNORDERED, Characteristics.CONCURRENT).getSet();

    private JImmutableCollectors()
    {
    }

    /**
     * Collects values into a JImmutableList.
     */
    @Nonnull
    public static  Collector> toList()
    {
        return new CollectorImpl<>(ORDERED,
                                   JImmutables.list(),
                                   (a, v) -> a.insert(v),
                                   (a, b) -> a.insertAll(b));
    }

    /**
     * Collects values into a JImmutableRandomAccessList.
     */
    @Nonnull
    public static  Collector> toRalist()
    {
        return new CollectorImpl<>(ORDERED,
                                   JImmutables.ralist(),
                                   (a, v) -> a.insert(v),
                                   (a, b) -> a.insertAll(b));
    }

    /**
     * Collects values into a hashed JImmutableSet.
     */
    @Nonnull
    public static  Collector> toSet()
    {
        return new CollectorImpl<>(UNORDERED,
                                   JImmutables.set(),
                                   (a, v) -> a.insert(v),
                                   (a, b) -> a.insertAll(b));
    }

    /**
     * Collects values into a sorted JImmutableSet using natural sort order of elements.
     */
    @Nonnull
    public static > Collector> toSortedSet()
    {
        return new CollectorImpl<>(UNORDERED,
                                   JImmutables.sortedSet(),
                                   (a, v) -> a.insert(v),
                                   (a, b) -> a.insertAll(b));
    }

    /**
     * Collects values into a sorted JImmutableSet using specified Comparator.
     */
    @Nonnull
    public static  Collector> toSortedSet(@Nonnull Comparator comparator)
    {
        return new CollectorImpl<>(UNORDERED,
                                   JImmutables.sortedSet(comparator),
                                   (a, v) -> a.insert(v),
                                   (a, b) -> a.insertAll(b));
    }

    /**
     * Collects values into a hashed JImmutableListMap using the specified classifier function
     * to generate keys from the encountered elements.
     */
    @Nonnull
    public static  Collector> groupingBy(@Nonnull Function classifier)
    {
        return new CollectorImpl<>(ORDERED,
                                   JImmutables.listMap(),
                                   (a, v) -> a.insert(classifier.apply(v), v),
                                   (a, b) -> combine(a, b));
    }

    private static  JImmutableListMap combine(@Nonnull JImmutableListMap a,
                                                          @Nonnull JImmutableListMap b)
    {
        for (JImmutableMap.Entry> e : b) {
            a = a.assign(e.getKey(), a.getList(e.getKey()).insertAll(e.getValue()));
        }
        return a;
    }

    private static class Accumulator
    {
        private Func2 adder;
        private Func2 combiner;
        private C list;

        private Accumulator(@Nonnull Func2 adder,
                            @Nonnull Func2 combiner,
                            @Nonnull C list)
        {
            this.adder = adder;
            this.combiner = combiner;
            this.list = list;
        }

        private synchronized void add(T value)
        {
            list = adder.apply(list, value);
        }

        private synchronized Accumulator combine(Accumulator other)
        {
            list = combiner.apply(list, other.list);
            return this;
        }
    }

    @Immutable
    private static class CollectorImpl
        implements Collector, C>
    {
        private final Set characteristics;
        private final C empty;
        private final Func2 adder;
        private final Func2 combiner;

        private CollectorImpl(@Nonnull Set characteristics,
                              @Nonnull C empty,
                              @Nonnull Func2 adder,
                              @Nonnull Func2 combiner)
        {
            this.characteristics = characteristics;
            this.empty = empty;
            this.adder = adder;
            this.combiner = combiner;
        }

        @Override
        public Supplier> supplier()
        {
            return () -> new Accumulator<>(adder, combiner, empty);
        }

        @Override
        public BiConsumer, T> accumulator()
        {
            return (a, v) -> a.add(v);
        }

        @Override
        public BinaryOperator> combiner()
        {
            return (left, right) -> left.combine(right);
        }

        @Override
        public Function, C> finisher()
        {
            return a -> a.list;
        }

        @Override
        public Set characteristics()
        {
            return characteristics;
        }
    }
}