code: public static <K, V> void validateNotNull(K key, V value1, V value2) {
          checkNotNull(key, NULL_KEY_IS_NOT_ALLOWED);
          checkNotNull(value1, NULL_VALUE_IS_NOT_ALLOWED);
          checkNotNull(value2, NULL_VALUE_IS_NOT_ALLOWED);
      }
docs: Validates that key and multi values are not null.
  
  @param key    the key to be validated.
  @param value1 first value to be validated.
  @param value2 second value to be validated.
  @param <K>    the type of key.
  @param <V>    the type of value.
  @throws java.lang.NullPointerException if key or any value is null.