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Jenetics - Java Genetic Algorithm Library

There is a newer version: 8.1.0

/*
 * Java Genetic Algorithm Library (jenetics-7.1.2).
 * Copyright (c) 2007-2023 Franz Wilhelmstötter
 *
 * 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.
 *
 * Author:
 *    Franz Wilhelmstötter ([email protected])
 */
package io.jenetics.util;

import static java.util.Objects.requireNonNull;

import java.util.Set;
import java.util.function.Supplier;
import java.util.stream.Collector;

/**
 * @param  the type of input elements to the accumulate operation
 * @param  the accumulator type
 * @param  the result type of the accumulated operation
 *
 * @author Franz Wilhelmstötter
 * @version 6.1
 * @since 6.1
 */
final class CollectorAccumulator
	implements Accumulator, R>
{

	private final Collector _collector;
	private A _collection;

	CollectorAccumulator(final Collector collector) {
		_collector = requireNonNull(collector);
	}

	@Override
	public CollectorAccumulator
	combine(final CollectorAccumulator other) {
		if (_collection == null) {
			_collection = _collector.supplier().get();
		}

		_collector.combiner().apply(_collection, other._collection);
		return this;
	}

	@Override
	public void accept(final T value) {
		if (_collection == null) {
			_collection = _collector.supplier().get();
		}
		_collector.accumulator().accept(_collection, value);
	}

	@Override
	public R result() {
		return _collector.finisher().apply(_collection);
	}

	@Override
	public Supplier> supplier() {
		return () -> new CollectorAccumulator<>(_collector);
	}

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

}