Method merge

guava/src/com/google/common/collect/TreeRangeMap.java:283–335

@since 28.1

(
      Range<K> range,
      @Nullable V value,
      BiFunction<? super V, ? super @Nullable V, ? extends @Nullable V> remappingFunction)

   * @since 28.1
   */
  @Override
  public void merge(
      Range<K> range,
      @Nullable V value,
      BiFunction<? super V, ? super @Nullable V, ? extends @Nullable V> remappingFunction) {
    checkNotNull(range);
    checkNotNull(remappingFunction);

    if (range.isEmpty()) {
      return;
    }
    split(range.lowerBound);
    split(range.upperBound);

    // Due to the splitting of any entries spanning the range bounds, we know that any entry with a
    // lower bound in the merge range is entirely contained by the merge range.
    Set<Entry<Cut<K>, RangeMapEntry<K, V>>> entriesInMergeRange =
        entriesByLowerBound.subMap(range.lowerBound, range.upperBound).entrySet();

    // Create entries mapping any unmapped ranges in the merge range to the specified value.
    ImmutableMap.Builder<Cut<K>, RangeMapEntry<K, V>> gaps = ImmutableMap.builder();
    if (value != null) {
      Iterator<Entry<Cut<K>, RangeMapEntry<K, V>>> backingItr = entriesInMergeRange.iterator();
      Cut<K> lowerBound = range.lowerBound;
      while (backingItr.hasNext()) {
        RangeMapEntry<K, V> entry = backingItr.next().getValue();
        Cut<K> upperBound = entry.getLowerBound();
        if (!lowerBound.equals(upperBound)) {
          gaps.put(lowerBound, new RangeMapEntry<K, V>(lowerBound, upperBound, value));
        }
        lowerBound = entry.getUpperBound();
      }
      if (!lowerBound.equals(range.upperBound)) {
        gaps.put(lowerBound, new RangeMapEntry<K, V>(lowerBound, range.upperBound, value));
      }
    }

    // Remap all existing entries in the merge range.
    Iterator<Entry<Cut<K>, RangeMapEntry<K, V>>> backingItr = entriesInMergeRange.iterator();
    while (backingItr.hasNext()) {
      Entry<Cut<K>, RangeMapEntry<K, V>> entry = backingItr.next();
      V newValue = remappingFunction.apply(entry.getValue().getValue(), value);
      if (newValue == null) {
        backingItr.remove();
      } else {
        entry.setValue(
            new RangeMapEntry<K, V>(
                entry.getValue().getLowerBound(), entry.getValue().getUpperBound(), newValue));
      }
    }

    entriesByLowerBound.putAll(gaps.build());
  }

  @Override
  public Map<Range<K>, V> asMapOfRanges() {