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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.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//     Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
//
//     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
//     distribution.
//
//     Neither the name of the Burton Computer Corporation nor the names
//     of its contributors may be used to endorse or promote products
//     derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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package org.javimmutable.collections.tree;

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.cursors.StandardCursor;
import org.javimmutable.collections.iterators.EmptyIterator;

import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;
import java.util.Collection;
import java.util.Comparator;

@Immutable
public class EmptyNode
    extends TreeNode
{
    static final EmptyNode INSTANCE = new EmptyNode();

    private EmptyNode()
    {
    }

    @SuppressWarnings("unchecked")
    public static  EmptyNode of()
    {
        return (EmptyNode)INSTANCE;
    }

    @Override
    public V getValueOr(Comparator props,
                        K key,
                        V defaultValue)
    {
        return defaultValue;
    }

    @Override
    public Holder find(Comparator props,
                          K key)
    {
        return Holders.of();
    }

    @Override
    public Holder> findEntry(Comparator props,
                                                       K key)
    {
        return Holders.of();
    }

    @Override
    public void addEntriesTo(Collection> collection)
    {
    }

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

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

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

    @Override
    int verifyDepthsMatch()
    {
        return 0;
    }

    @Override
    K getMaxKey()
    {
        return null;
    }

    @Override
    UpdateResult assignImpl(Comparator props,
                                  K key,
                                  V value)
    {
        return UpdateResult.createInPlace(new LeafNode(key, value), 1);
    }

    @Override
    DeleteResult deleteImpl(Comparator props,
                                  K key)
    {
        return DeleteResult.createUnchanged();
    }

    @Override
    DeleteMergeResult leftDeleteMerge(TreeNode node)
    {
        throw new UnsupportedOperationException();
    }

    @Override
    DeleteMergeResult rightDeleteMerge(TreeNode node)
    {
        throw new UnsupportedOperationException();
    }
}