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Library providing immutable/persistent collection classes for Java. While collections are immutable they provide methods for adding and removing values by creating new modified copies of themselves. Each copy shares almost all of its structure with other copies to minimize memory consumption.

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///###////////////////////////////////////////////////////////////////////////
//
// Burton Computer Corporation
// http://www.burton-computer.com
//
// Copyright (c) 2017, Burton Computer Corporation
// All rights reserved.
//
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//
//     Redistributions of source code must retain the above copyright
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//
//     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
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//     of its contributors may be used to endorse or promote products
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package org.javimmutable.collections.array;

import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.Holders;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.SplitableIterator;
import org.javimmutable.collections.common.MutableDelta;
import org.javimmutable.collections.cursors.StandardCursor;
import org.javimmutable.collections.iterators.EmptyIterator;

import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;

@Immutable
public class EmptyTrieNode
    extends TrieNode
{
    private static final EmptyTrieNode EMPTY = new EmptyTrieNode();

    @SuppressWarnings("unchecked")
    static  EmptyTrieNode instance()
    {
        return (EmptyTrieNode)EMPTY;
    }

    @Override
    public boolean isEmpty()
    {
        return true;
    }

    @Override
    public T getValueOr(int shift,
                        int index,
                        T defaultValue)
    {
        return defaultValue;
    }

    @Override
    public Holder find(int shift,
                          int index)
    {
        return Holders.of();
    }

    @Override
    public TrieNode assign(int shift,
                              int index,
                              T value,
                              MutableDelta sizeDelta)
    {
        sizeDelta.add(1);
        return LeafTrieNode.of(index, value);
    }

    @Override
    public TrieNode delete(int shift,
                              int index,
                              MutableDelta sizeDelta)
    {
        return this;
    }

    @Override
    public int getShift()
    {
        return 0;
    }

    @Override
    public boolean isLeaf()
    {
        return true;
    }

    @Override
    public TrieNode paddedToMinimumDepthForShift(int shift)
    {
        return this;
    }

    @Nonnull
    @Override
    public Cursor> cursor()
    {
        return StandardCursor.of();
    }

    @Nonnull
    @Override
    public SplitableIterator> iterator()
    {
        return EmptyIterator.of();
    }

    @Override
    public void checkInvariants()
    {
    }
}