Method putAll

lib/java/util/HashMap.java:615–620

Copies all the mappings in the specified map to this map. These mappings will replace all mappings that this map had for any of the keys currently in the given map. @param map the map to copy mappings from. @throws NullPointerException if map is null.

(Map<? extends K, ? extends V> map)

     *             if {@code map} is {@code null}.
     */
    @Override
    public void putAll(Map<? extends K, ? extends V> map) {
        if (!map.isEmpty()) {
            putAllImpl(map);
        }
    }

    private void putAllImpl(Map<? extends K, ? extends V> map) {
        int capacity = elementCount + map.size();