org.eclipse.collections.impl.block.procedure.NonMutatingAggregationProcedure Maven / Gradle / Ivy

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/*
 * Copyright (c) 2016 Goldman Sachs.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v. 1.0 which accompany this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 */

package org.eclipse.collections.impl.block.procedure;

import org.eclipse.collections.api.block.function.Function;
import org.eclipse.collections.api.block.function.Function0;
import org.eclipse.collections.api.block.function.Function2;
import org.eclipse.collections.api.block.procedure.Procedure;
import org.eclipse.collections.api.map.MutableMap;

/**
 * This procedure is used to apply an aggregate function like sum on a grouped set of data.  The values in the
 * grouping must be immutable using this procedure.  An example would be using an Integer which is immutable
 * vs. an AtomicInteger which is not.
 */
public final class NonMutatingAggregationProcedure implements Procedure
{
    private static final long serialVersionUID = 1L;
    private final MutableMap map;
    private final Function groupBy;
    private final Function0 zeroValueFactory;
    private final Function2 nonMutatingAggregator;

    public NonMutatingAggregationProcedure(MutableMap map, Function groupBy, Function0 zeroValueFactory, Function2 nonMutatingAggregator)
    {
        this.map = map;
        this.groupBy = groupBy;
        this.zeroValueFactory = zeroValueFactory;
        this.nonMutatingAggregator = nonMutatingAggregator;
    }

    @Override
    public void value(T each)
    {
        K key = this.groupBy.valueOf(each);
        this.map.updateValueWith(key, this.zeroValueFactory, this.nonMutatingAggregator, each);
    }
}