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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
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// Copyright (c) 2017, Burton Computer Corporation
// All rights reserved.
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package org.javimmutable.collections.hash.collision_map;

import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.SplitableIterator;
import org.javimmutable.collections.common.MutableDelta;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

/**
 * Interface for transformation objects that manage the leaf nodes in the hash table.
 * Implementations are free to use any class for their leaf nodes and manage them as needed.
 * NOTE: The transforms object is shared across all versions of a hash table so it MUST BE IMMUTABLE.
 * If the transforms object is not immutable it can cause the table to become
 * corrupted over time and/or make older versions of the table invalid.
 */
public interface CollisionMap
{
    /**
     * Take the current leaf object (if there is one) and produce a new one
     * (possibly the same) with the specified key and value.  If there is not currently
     * a leaf for this key in the array the leaf will be null.  The result must be
     * a non-null leaf object with the specified value associated with the specified key.
     * If this key was not previously present the method must add 1 to the delta
     * so that the size of the array can be properly maintained.
     */
    @Nonnull
    T update(@Nullable T leaf,
             @Nonnull K key,
             @Nullable V value,
             @Nonnull MutableDelta delta);

    /**
     * Take the current leaf object and produce a new one (possibly the same)
     * with the specified key removed.  If the key was previously present in the leaf
     * the method must subtract 1 from the delta so that the size of the array can be
     * properly maintained.  The returned leaf will be null of no values remain after
     * the deletion.
     */
    @Nullable
    T delete(@Nonnull T leaf,
             @Nonnull K key,
             @Nonnull MutableDelta delta);

    /**
     * Look for the specified key in the leaf object and return a Holder
     * that is empty if the key is not in the leaf or else contains the value associated
     * with the key.
     */
    V getValueOr(@Nonnull T leaf,
                 @Nonnull K key,
                 V defaultValue);

    /**
     * Look for the specified key in the leaf object and return a Holder
     * that is empty if the key is not in the leaf or else contains the value associated
     * with the key.
     */
    Holder findValue(@Nonnull T leaf,
                        @Nonnull K key);

    /**
     * Look for the specified key in the leaf object and return a Holder
     * that is empty if the key is not in the leaf or else contains a JImmutableMap.Entry
     * associated with the key and value.
     */
    Holder> findEntry(@Nonnull T leaf,
                                                @Nonnull K key);

    /**
     * Return a (possibly empty) Cursor over all of the JImmutableMap.Entries
     * in the specified leaf object.
     */
    Cursor> cursor(@Nonnull T leaf);

    /**
     * Return a (possibly empty) SplitableIterator over all of the JImmutableMap.Entries
     * in the specified leaf object.
     */
    SplitableIterator> iterator(@Nonnull T leaf);
}