Method merge

vm/JavaAPI/src/java/util/Map.java:421–421

If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value; otherwise replaces the associated value with the results of the remapping function, or removes if the result is null.

(K key, V value,
            BiFunction<? super V, ? super V, ? extends V> remappingFunction)

     * remapping function, or removes if the result is {@code null}.
     */
    default V merge(K key, V value,
            BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
        if (remappingFunction == null || value == null) {
            throw new NullPointerException();