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package norswap.utils.multimap;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;

/**
 * A straightfoward multimap implementation based on {@link HashMap}.
 * 
 * The implementation uses array lists as collections, so duplicate values are permitted.
 * It is safe to cast the (collection) values to {@link java.util.List}.
 */
public final class MultiHashMap extends AbstractMultiHashMap
{
    // ---------------------------------------------------------------------------------------------

    @Override ArrayList newCollection ()
    {
        return new ArrayList<>();
    }

    // ---------------------------------------------------------------------------------------------

    @Override Collection emptyCollection ()
    {
        return Collections.emptyList();
    }

    // ---------------------------------------------------------------------------------------------
}