org.apache.james.util.streams.JamesCollectors.java Source code

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 * distributed with this work for additional information        *
 * regarding copyright ownership.  The ASF licenses this file   *
 * to you under the Apache License, Version 2.0 (the            *
 * "License"); you may not use this file except in compliance   *
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package org.apache.james.util.streams;

import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.Collector;
import java.util.stream.Collectors;

import com.google.common.base.Preconditions;

public class JamesCollectors {
    public static <D> Collector<D, ?, Map<Integer, List<D>>> chunker(int chunkSize) {
        Preconditions.checkArgument(chunkSize > 0, "ChunkSize should be strictly positive");
        AtomicInteger counter = new AtomicInteger(-1);
        return Collectors.groupingBy(x -> counter.incrementAndGet() / chunkSize);
    }
}