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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) 2013, 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
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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.cursors.SingleValueCursor;

import java.util.Collection;
import java.util.Comparator;

public class LeafNode
        extends TreeNode
        implements JImmutableMap.Entry,
                   Holder
{
    private final K nodeKey;
    private final V value;

    public LeafNode(K key,
                    V value)
    {
        this.nodeKey = key;
        this.value = value;
    }

    public K getKey()
    {
        return nodeKey;
    }

    public V getValue()
    {
        return value;
    }

    public boolean isEmpty()
    {
        return false;
    }

    public boolean isFilled()
    {
        return true;
    }

    public V getValueOrNull()
    {
        return value;
    }

    public V getValueOr(V defaultValue)
    {
        return value;
    }

    @Override
    public Holder find(Comparator props,
                          K searchKey)
    {
        return props.compare(searchKey, nodeKey) == 0 ? this : Holders.of();
    }

    @Override
    public Holder> findEntry(Comparator props,
                                                       K searchKey)
    {
        return props.compare(searchKey, nodeKey) == 0 ? Holders.>of(this) : Holders.>of();
    }

    @Override
    public K getMaxKey()
    {
        return nodeKey;
    }

    @Override
    public UpdateResult update(Comparator props,
                                     K key,
                                     V value)
    {
        final int diff = props.compare(key, nodeKey);
        if (diff == 0) {
            if (this.value == value) { // value identity - useful for sets, booleans, etc
                return UpdateResult.createUnchanged();
            } else {
                return UpdateResult.createInPlace(new LeafNode(key, value), 0);
            }
        } else if (diff < 0) {
            return UpdateResult.createSplit(new LeafNode(key, value), this, 1);
        } else {
            return UpdateResult.createSplit(this, new LeafNode(key, value), 1);
        }
    }

    @Override
    public void addEntriesTo(Collection> collection)
    {
        collection.add(this);
    }

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

    @Override
    public DeleteResult delete(Comparator props,
                                     K key)
    {
        if (props.compare(key, nodeKey) == 0) {
            return DeleteResult.createEliminated();
        } else {
            return DeleteResult.createUnchanged();
        }
    }

    @Override
    public DeleteMergeResult leftDeleteMerge(Comparator props,
                                                   TreeNode node)
    {
        return new DeleteMergeResult(new TwoNode(node,
                                                             this,
                                                             node.getMaxKey(),
                                                             nodeKey));
    }

    @Override
    public DeleteMergeResult rightDeleteMerge(Comparator props,
                                                    TreeNode node)
    {
        return new DeleteMergeResult(new TwoNode(this,
                                                             node,
                                                             nodeKey,
                                                             node.getMaxKey()));
    }

    @Override
    public String toString()
    {
        return String.format("%s => %s", nodeKey, value);
    }

    @Override
    public Cursor> cursor()
    {
        return SingleValueCursor.>of(this);
    }

    @SuppressWarnings("RedundantIfStatement")
    @Override
    public boolean equals(Object o)
    {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        LeafNode leafNode = (LeafNode)o;

        if (nodeKey != null ? !nodeKey.equals(leafNode.nodeKey) : leafNode.nodeKey != null) {
            return false;
        }
        if (value != null ? !value.equals(leafNode.value) : leafNode.value != null) {
            return false;
        }

        return true;
    }

    @Override
    public int hashCode()
    {
        int result = nodeKey != null ? nodeKey.hashCode() : 0;
        result = 31 * result + (value != null ? value.hashCode() : 0);
        return result;
    }
}