* nullness checker.
           */
          K key = keyFunction.apply(t);
          V newValue = valueFunction.apply(t);
          accum.put(
              checkNotNull(key, "Null key for input %s", t),
              checkNotNull(newValue, "Null value for input %s", t));
        },
        EnumMapAccumulator::combine,
        EnumMapAccumulator::toImmutableMap,

           * nullness checker.
           */
          K key = keyFunction.apply(t);
          V newValue = valueFunction.apply(t);
          accum.put(
              checkNotNull(key, "Null key for input %s", t),
              checkNotNull(newValue, "Null value for input %s", t));
        },
        EnumMapAccumulator::combine,
        EnumMapAccumulator::toImmutableMap,

    }

    @Override
    @Nullable V getValue(int index) {
      return at(index, columnIndex);
    }

    @Override
    @Nullable V setValue(int index, @Nullable V newValue) {
      return set(index, columnIndex, newValue);
    }
  }

  /**
   * Returns an immutable set of the valid column keys, including those that are associated with
   * null values only.
   *

      long oldValue;
      long newValue;
      do {
        oldValue = data.get(longIndex);
        newValue = oldValue | mask;
        if (oldValue == newValue) {
          return false;
        }
      } while (!data.compareAndSet(longIndex, oldValue, newValue));

      // We turned the bit on, so increment bitCount.
      bitCount.increment();

        return parent.remove(toCamelCase(key), value);
    }

    @Override
    public boolean replace(final K key, final V oldValue, final V newValue) {
        if (parent.replace(key, oldValue, newValue)) {
            return true;
        }
        return parent.replace(key, oldValue, newValue);
    }

    @Override
    public V replace(final K key, final V value) {
        // use original key

    V oldValue = table.get(row, column);
    if (oldValue == null) {
      table.put(row, column, value);
    } else {
      V newValue = mergeFunction.apply(oldValue, value);
      if (newValue == null) {
        table.remove(row, column);
      } else {
        table.put(row, column, newValue);
      }
    }
  }

  private TableCollectors() {}

        if (!escape) {
            return value;
        }

        String newValue = value;
        for (final String element : Constants.RESERVED) {
            final String replacement = element.replaceAll("(.)", "\\\\$1");
            newValue = newValue.replace(element, replacement);
        }
        return newValue;
    }

    /**
     * Builds the complete query string from the configured parameters.

    V oldValue = table.get(row, column);
    if (oldValue == null) {
      table.put(row, column, value);
    } else {
      V newValue = mergeFunction.apply(oldValue, value);
      if (newValue == null) {
        table.remove(row, column);
      } else {
        table.put(row, column, newValue);
      }
    }
  }

  private TableCollectors() {}

      V value = localCache.get(key);
      if (value != null) {
        return value;
      }

      try {
        V newValue = valueLoader.call();
        localCache.put(key, newValue);
        return newValue;
      } catch (Exception e) {
        throw new ExecutionException(e);
      }
    }

    @Override
    public @Nullable V getIfPresent(Object key) {

    assertNull(map.putInstance(Integer.class, new Integer(5)));

    Integer oldValue = map.putInstance(Integer.class, new Integer(7));
    assertEquals(5, (int) oldValue);

    Integer newValue = map.getInstance(Integer.class);
    assertEquals(7, (int) newValue);

    // Won't compile: map.putInstance(Double.class, new Long(42));
  }

  public void testNull() {