Package org.djutils.multikeymap

Class MultiKeyMap<T>

  • Type Parameters:
    T - value type
    public class MultiKeyMap<T>
extends Object
    Store for data indexed by a combination of objects. An important difference with a normal (Linked-)HashMap is that the getValue method has a Supplier argument that will be invoked when no value was stored under the provided combination of keys. The value yielded by the Supplier is then stored under that key combination. If this behavior is not wanted, the user can provide the null value for the Supplier argument. The map can store null values, but on retrieval these are indistinguishable from values that were never set. No key values may be null.

    Copyright (c) 2013-2021 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved.
    BSD-style license. See DJUTILS License.

    Version:
    $Revision$, $LastChangedDate$, by $Author$, initial version 20 apr. 2018
    Author:
    Alexander Verbraeck, Peter Knoppers, Wouter Schakel

    • Constructor Detail

      • MultiKeyMap

        public MultiKeyMap​(Class<?>... keyTypes)
        Construct a new MultiKeyMap.
        Parameters:
        keyTypes - Class<?>...; the types of the keys

    • Method Detail

      • get

        public T get​(Supplier<T> supplier,
             Object... keys)
        Retrieve a value from this MultiKeyMap. Can create a new entry if it does not exist yet.
        Parameters:
        supplier - Supplier<T>; supplier of T in case the leaf does not exist yet. Set this to null to suppress creation of new branches and a new leaf
        keys - Object...; list of key objects
        Returns:
        T; the existing value, or the value that was obtained through the supplier. Returns null if the leaf does not exist and supplier is null

      • get

        public T get​(Object... keys)
        Retrieve a value from this MultiKeyMap.
        Parameters:
        keys - Object...; the key objects
        Returns:
        T; value, or null if no value is stored under the provided key objects

      • getSubMap

        public MultiKeyMap<T> getSubMap​(Object... keys)
        Retrieve a sub map.
        Parameters:
        keys - Object...; the key objects (must be at least one item shorter than the full depth)
        Returns:
        MultiKeyMap<T>; the sub map

      • put

        public T put​(T newValue,
             Object... keys)
        Put (add or replace) a value in this MultiKeyMap.
        Parameters:
        newValue - T; the new value
        keys - Object...; the key objects
        Returns:
        T; the previous value stored under the key objects, or null if no value was currently stored under the key objects

      • getKeys

        public Set<Object> getKeys​(Object... keys)
        Return set of key objects on this level.
        Parameters:
        keys - Object...; list of key objects (may be empty to select the key set at the top level
        Returns:
        Set; set of key objects on this level. This is not a safe copy; this set reflects subsequent changes in this MultiKeyMap and modifying this set would modify this MultiKeyMap (potentially making it inconsistent).

      • clear

        public Object clear​(Object... keys)
        Clears the mapping for a key combination.
        Parameters:
        keys - Object...; key combination to clear the map for
        Returns:
        Object; object that was previously mapped to the key combination, or null if it was not cached.