org.opentripplanner.netex.index.api.ReadOnlyHierarchicalMap Maven / Gradle / Ivy

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package org.opentripplanner.netex.index.api;

import java.util.Collection;

/**
 * Read only interface for a hierarchical map. This interface proved a interface to a hierarchy of
 * maps with a parent - child relationship. Elements are retrieved using ({@link #lookup(Object)}).
 * The lookup call check the current instance, then the parent to find an element. This continue
 * until the root of the hierarchy is reached. If a {@code key} exist in more than two places in the
 * hierarchy, the first value found wins.
 *
 * @param  The key type
 * @param  Thr value type
 */
public interface ReadOnlyHierarchicalMap {
  /**
   * Lookup element, if not found delegate up to the parent. NB! elements of this class and its
   * parents are NOT merged, the closest win.
   *
   * @return an empty collection if no element are found.
   */
  V lookup(K key);

  /**
   * The key exist in this Collection or one of the parents (parent, parent´s parent and so on)
   */
  boolean containsKey(K key);

  /**
   * @return a collection of all values hold in the local map, all values added to one of the
   * parents are excluded from the collection.
   */
  Collection localKeys();

  /**
   * @return a collection of all values hold in the local map, all values added to one of the
   * parents are excluded from the collection.
   */
  Collection localValues();

  /**
   * @return {@code true} if no local elements exist.
   */
  boolean localIsEmpty();
}