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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) 2014, Burton Computer Corporation
// All rights reserved.
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package org.javimmutable.collections;

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

/**
 * Interface for maps that map keys to lists of values.
 *
 * @param 
 * @param 
 */
@Immutable
public interface JImmutableListMap
        extends Insertable>,
                Mapped>,
                Iterable>>,
                Cursorable>>
{
    /**
     * Return the list associated with key or an empty list if no list is associated.
     *
     * @param key identifies the value to retrieve
     * @return list associated with key or an empty list if no value is associated
     */
    @Nonnull
    JImmutableList getList(@Nonnull K key);

    /**
     * Sets the list associated with a specific key.  Key and value must be non-null.
     * If the key already has a list in the map the old list is discarded
     * and the new list is stored in its place.  Returns a new JImmutableListMap reflecting
     * any changes.  The original map is always left unchanged.
     *
     * @param key   non-null key
     * @param value list of possibly null values to use for this key
     * @return new map reflecting the change
     */
    @Nonnull
    JImmutableListMap assign(@Nonnull K key,
                                   @Nonnull JImmutableList value);

    /**
     * Add key/value entry to the map, replacing any existing entry with same key.
     *
     * @param value
     * @return
     */
    @Nonnull
    @Override
    Insertable> insert(@Nonnull JImmutableMap.Entry value);

    /**
     * Add value to the list for the specified key.  Note that this can create duplicate values
     * in the list.
     *
     * @param value
     * @param value
     * @return
     */
    @Nonnull
    JImmutableListMap insert(@Nonnull K key,
                                   @Nullable V value);

    /**
     * Deletes the entry for the specified key (if any).  Returns a new map if the value
     * was deleted or the current map if the key was not contained in the map.
     *
     * @param key non-null key
     * @return same or different map depending on whether key was removed
     */
    @Nonnull
    JImmutableListMap delete(@Nonnull K key);

    /**
     * Return the number of keys in the map.
     *
     * @return
     */
    int size();

    /**
     * @return true only if list contains no values
     */
    boolean isEmpty();

    /**
     * @return an equivalent collection with no values
     */
    @Nonnull
    JImmutableListMap deleteAll();

    /**
     * Creates a Cursor to access all of the Map's keys.
     *
     * @return
     */
    @Nonnull
    Cursor keysCursor();

    /**
     * Creates a Cursor to access all of the specified key's list.
     * If no list exists for key an empty cursor is returned.
     *
     * @return a (possibly empty) cursor for traversing the values associated with key
     */
    @Nonnull
    Cursor valuesCursor(@Nonnull K key);
}