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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) 2018, 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
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//     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
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package org.javimmutable.collections.list;

import org.javimmutable.collections.Cursor;
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.Iterator;

/**
 * Node implementation containing no values.  Implemented as a singleton.
 */
@Immutable
final class EmptyNode
    implements Node
{
    private static final EmptyNode INSTANCE = new EmptyNode();

    private EmptyNode()
    {
    }

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

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

    @Override
    public boolean isFull()
    {
        return false;
    }

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

    @Override
    public int getDepth()
    {
        return 1;
    }

    @Override
    public Node deleteFirst()
    {
        throw new IllegalStateException();
    }

    @Override
    public Node deleteLast()
    {
        throw new IllegalStateException();
    }

    @Override
    public Node insertFirst(T value)
    {
        return new LeafNode(value);
    }

    @Override
    public Node insertLast(T value)
    {
        return new LeafNode(value);
    }

    @Override
    public boolean containsIndex(int index)
    {
        return false;
    }

    @Override
    public T get(int index)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public Node assign(int index,
                          T value)
    {
        throw new IndexOutOfBoundsException();
    }

    @Override
    public Node insertAll(int maxSize,
                             boolean forwardOrder,
                             @Nonnull Iterator values)
    {
        return TreeBuilder.createFromIterator(maxSize, forwardOrder, values);
    }

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

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

    @Override
    public void checkInvariants()
    {
        //TODO: fix empty checkInvariants()
    }
}