001/*
002 * Copyright (C) 2012 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.collect;
016
017import static com.google.common.base.Preconditions.checkArgument;
018import static com.google.common.base.Preconditions.checkElementIndex;
019import static com.google.common.base.Preconditions.checkNotNull;
020import static com.google.common.collect.SortedLists.KeyAbsentBehavior.NEXT_HIGHER;
021import static com.google.common.collect.SortedLists.KeyAbsentBehavior.NEXT_LOWER;
022import static com.google.common.collect.SortedLists.KeyPresentBehavior.ANY_PRESENT;
023import static java.util.Objects.requireNonNull;
024
025import com.google.common.annotations.GwtIncompatible;
026import com.google.common.annotations.J2ktIncompatible;
027import com.google.common.collect.SortedLists.KeyAbsentBehavior;
028import com.google.common.collect.SortedLists.KeyPresentBehavior;
029import com.google.common.primitives.Ints;
030import com.google.errorprone.annotations.CanIgnoreReturnValue;
031import com.google.errorprone.annotations.DoNotCall;
032import com.google.errorprone.annotations.concurrent.LazyInit;
033import java.io.InvalidObjectException;
034import java.io.ObjectInputStream;
035import java.io.Serializable;
036import java.util.Collections;
037import java.util.Iterator;
038import java.util.List;
039import java.util.NoSuchElementException;
040import java.util.Set;
041import java.util.stream.Collector;
042import javax.annotation.CheckForNull;
043
044/**
045 * A {@link RangeSet} whose contents will never change, with many other important properties
046 * detailed at {@link ImmutableCollection}.
047 *
048 * @author Louis Wasserman
049 * @since 14.0
050 */
051@GwtIncompatible
052@ElementTypesAreNonnullByDefault
053public final class ImmutableRangeSet<C extends Comparable> extends AbstractRangeSet<C>
054    implements Serializable {
055
056  private static final ImmutableRangeSet<Comparable<?>> EMPTY =
057      new ImmutableRangeSet<>(ImmutableList.<Range<Comparable<?>>>of());
058
059  private static final ImmutableRangeSet<Comparable<?>> ALL =
060      new ImmutableRangeSet<>(ImmutableList.of(Range.<Comparable<?>>all()));
061
062  /**
063   * Returns a {@code Collector} that accumulates the input elements into a new {@code
064   * ImmutableRangeSet}. As in {@link Builder}, overlapping ranges are not permitted and adjacent
065   * ranges will be merged.
066   *
067   * @since 23.1
068   */
069  public static <E extends Comparable<? super E>>
070      Collector<Range<E>, ?, ImmutableRangeSet<E>> toImmutableRangeSet() {
071    return CollectCollectors.toImmutableRangeSet();
072  }
073
074  /**
075   * Returns an empty immutable range set.
076   *
077   * <p><b>Performance note:</b> the instance returned is a singleton.
078   */
079  @SuppressWarnings("unchecked")
080  public static <C extends Comparable> ImmutableRangeSet<C> of() {
081    return (ImmutableRangeSet<C>) EMPTY;
082  }
083
084  /**
085   * Returns an immutable range set containing the specified single range. If {@link Range#isEmpty()
086   * range.isEmpty()}, this is equivalent to {@link ImmutableRangeSet#of()}.
087   */
088  public static <C extends Comparable> ImmutableRangeSet<C> of(Range<C> range) {
089    checkNotNull(range);
090    if (range.isEmpty()) {
091      return of();
092    } else if (range.equals(Range.all())) {
093      return all();
094    } else {
095      return new ImmutableRangeSet<C>(ImmutableList.of(range));
096    }
097  }
098
099  /** Returns an immutable range set containing the single range {@link Range#all()}. */
100  @SuppressWarnings("unchecked")
101  static <C extends Comparable> ImmutableRangeSet<C> all() {
102    return (ImmutableRangeSet<C>) ALL;
103  }
104
105  /** Returns an immutable copy of the specified {@code RangeSet}. */
106  public static <C extends Comparable> ImmutableRangeSet<C> copyOf(RangeSet<C> rangeSet) {
107    checkNotNull(rangeSet);
108    if (rangeSet.isEmpty()) {
109      return of();
110    } else if (rangeSet.encloses(Range.<C>all())) {
111      return all();
112    }
113
114    if (rangeSet instanceof ImmutableRangeSet) {
115      ImmutableRangeSet<C> immutableRangeSet = (ImmutableRangeSet<C>) rangeSet;
116      if (!immutableRangeSet.isPartialView()) {
117        return immutableRangeSet;
118      }
119    }
120    return new ImmutableRangeSet<C>(ImmutableList.copyOf(rangeSet.asRanges()));
121  }
122
123  /**
124   * Returns an {@code ImmutableRangeSet} containing each of the specified disjoint ranges.
125   * Overlapping ranges and empty ranges are forbidden, though adjacent ranges are permitted and
126   * will be merged.
127   *
128   * @throws IllegalArgumentException if any ranges overlap or are empty
129   * @since 21.0
130   */
131  public static <C extends Comparable<?>> ImmutableRangeSet<C> copyOf(Iterable<Range<C>> ranges) {
132    return new ImmutableRangeSet.Builder<C>().addAll(ranges).build();
133  }
134
135  /**
136   * Returns an {@code ImmutableRangeSet} representing the union of the specified ranges.
137   *
138   * <p>This is the smallest {@code RangeSet} which encloses each of the specified ranges. Duplicate
139   * or connected ranges are permitted, and will be coalesced in the result.
140   *
141   * @since 21.0
142   */
143  public static <C extends Comparable<?>> ImmutableRangeSet<C> unionOf(Iterable<Range<C>> ranges) {
144    return copyOf(TreeRangeSet.create(ranges));
145  }
146
147  ImmutableRangeSet(ImmutableList<Range<C>> ranges) {
148    this.ranges = ranges;
149  }
150
151  private ImmutableRangeSet(ImmutableList<Range<C>> ranges, ImmutableRangeSet<C> complement) {
152    this.ranges = ranges;
153    this.complement = complement;
154  }
155
156  private final transient ImmutableList<Range<C>> ranges;
157
158  @Override
159  public boolean intersects(Range<C> otherRange) {
160    int ceilingIndex =
161        SortedLists.binarySearch(
162            ranges,
163            Range.<C>lowerBoundFn(),
164            otherRange.lowerBound,
165            Ordering.natural(),
166            ANY_PRESENT,
167            NEXT_HIGHER);
168    if (ceilingIndex < ranges.size()
169        && ranges.get(ceilingIndex).isConnected(otherRange)
170        && !ranges.get(ceilingIndex).intersection(otherRange).isEmpty()) {
171      return true;
172    }
173    return ceilingIndex > 0
174        && ranges.get(ceilingIndex - 1).isConnected(otherRange)
175        && !ranges.get(ceilingIndex - 1).intersection(otherRange).isEmpty();
176  }
177
178  @Override
179  public boolean encloses(Range<C> otherRange) {
180    int index =
181        SortedLists.binarySearch(
182            ranges,
183            Range.<C>lowerBoundFn(),
184            otherRange.lowerBound,
185            Ordering.natural(),
186            ANY_PRESENT,
187            NEXT_LOWER);
188    return index != -1 && ranges.get(index).encloses(otherRange);
189  }
190
191  @Override
192  @CheckForNull
193  public Range<C> rangeContaining(C value) {
194    int index =
195        SortedLists.binarySearch(
196            ranges,
197            Range.<C>lowerBoundFn(),
198            Cut.belowValue(value),
199            Ordering.natural(),
200            ANY_PRESENT,
201            NEXT_LOWER);
202    if (index != -1) {
203      Range<C> range = ranges.get(index);
204      return range.contains(value) ? range : null;
205    }
206    return null;
207  }
208
209  @Override
210  public Range<C> span() {
211    if (ranges.isEmpty()) {
212      throw new NoSuchElementException();
213    }
214    return Range.create(ranges.get(0).lowerBound, ranges.get(ranges.size() - 1).upperBound);
215  }
216
217  @Override
218  public boolean isEmpty() {
219    return ranges.isEmpty();
220  }
221
222  /**
223   * Guaranteed to throw an exception and leave the {@code RangeSet} unmodified.
224   *
225   * @throws UnsupportedOperationException always
226   * @deprecated Unsupported operation.
227   */
228  @Deprecated
229  @Override
230  @DoNotCall("Always throws UnsupportedOperationException")
231  public void add(Range<C> range) {
232    throw new UnsupportedOperationException();
233  }
234
235  /**
236   * Guaranteed to throw an exception and leave the {@code RangeSet} unmodified.
237   *
238   * @throws UnsupportedOperationException always
239   * @deprecated Unsupported operation.
240   */
241  @Deprecated
242  @Override
243  @DoNotCall("Always throws UnsupportedOperationException")
244  public void addAll(RangeSet<C> other) {
245    throw new UnsupportedOperationException();
246  }
247
248  /**
249   * Guaranteed to throw an exception and leave the {@code RangeSet} unmodified.
250   *
251   * @throws UnsupportedOperationException always
252   * @deprecated Unsupported operation.
253   */
254  @Deprecated
255  @Override
256  @DoNotCall("Always throws UnsupportedOperationException")
257  public void addAll(Iterable<Range<C>> other) {
258    throw new UnsupportedOperationException();
259  }
260
261  /**
262   * Guaranteed to throw an exception and leave the {@code RangeSet} unmodified.
263   *
264   * @throws UnsupportedOperationException always
265   * @deprecated Unsupported operation.
266   */
267  @Deprecated
268  @Override
269  @DoNotCall("Always throws UnsupportedOperationException")
270  public void remove(Range<C> range) {
271    throw new UnsupportedOperationException();
272  }
273
274  /**
275   * Guaranteed to throw an exception and leave the {@code RangeSet} unmodified.
276   *
277   * @throws UnsupportedOperationException always
278   * @deprecated Unsupported operation.
279   */
280  @Deprecated
281  @Override
282  @DoNotCall("Always throws UnsupportedOperationException")
283  public void removeAll(RangeSet<C> other) {
284    throw new UnsupportedOperationException();
285  }
286
287  /**
288   * Guaranteed to throw an exception and leave the {@code RangeSet} unmodified.
289   *
290   * @throws UnsupportedOperationException always
291   * @deprecated Unsupported operation.
292   */
293  @Deprecated
294  @Override
295  @DoNotCall("Always throws UnsupportedOperationException")
296  public void removeAll(Iterable<Range<C>> other) {
297    throw new UnsupportedOperationException();
298  }
299
300  @Override
301  public ImmutableSet<Range<C>> asRanges() {
302    if (ranges.isEmpty()) {
303      return ImmutableSet.of();
304    }
305    return new RegularImmutableSortedSet<>(ranges, Range.<C>rangeLexOrdering());
306  }
307
308  @Override
309  public ImmutableSet<Range<C>> asDescendingSetOfRanges() {
310    if (ranges.isEmpty()) {
311      return ImmutableSet.of();
312    }
313    return new RegularImmutableSortedSet<>(ranges.reverse(), Range.<C>rangeLexOrdering().reverse());
314  }
315
316  @LazyInit @CheckForNull private transient ImmutableRangeSet<C> complement;
317
318  private final class ComplementRanges extends ImmutableList<Range<C>> {
319    // True if the "positive" range set is empty or bounded below.
320    private final boolean positiveBoundedBelow;
321
322    // True if the "positive" range set is empty or bounded above.
323    private final boolean positiveBoundedAbove;
324
325    private final int size;
326
327    ComplementRanges() {
328      this.positiveBoundedBelow = ranges.get(0).hasLowerBound();
329      this.positiveBoundedAbove = Iterables.getLast(ranges).hasUpperBound();
330
331      int size = ranges.size() - 1;
332      if (positiveBoundedBelow) {
333        size++;
334      }
335      if (positiveBoundedAbove) {
336        size++;
337      }
338      this.size = size;
339    }
340
341    @Override
342    public int size() {
343      return size;
344    }
345
346    @Override
347    public Range<C> get(int index) {
348      checkElementIndex(index, size);
349
350      Cut<C> lowerBound;
351      if (positiveBoundedBelow) {
352        lowerBound = (index == 0) ? Cut.<C>belowAll() : ranges.get(index - 1).upperBound;
353      } else {
354        lowerBound = ranges.get(index).upperBound;
355      }
356
357      Cut<C> upperBound;
358      if (positiveBoundedAbove && index == size - 1) {
359        upperBound = Cut.<C>aboveAll();
360      } else {
361        upperBound = ranges.get(index + (positiveBoundedBelow ? 0 : 1)).lowerBound;
362      }
363
364      return Range.create(lowerBound, upperBound);
365    }
366
367    @Override
368    boolean isPartialView() {
369      return true;
370    }
371  }
372
373  @Override
374  public ImmutableRangeSet<C> complement() {
375    ImmutableRangeSet<C> result = complement;
376    if (result != null) {
377      return result;
378    } else if (ranges.isEmpty()) {
379      return complement = all();
380    } else if (ranges.size() == 1 && ranges.get(0).equals(Range.all())) {
381      return complement = of();
382    } else {
383      ImmutableList<Range<C>> complementRanges = new ComplementRanges();
384      result = complement = new ImmutableRangeSet<C>(complementRanges, this);
385    }
386    return result;
387  }
388
389  /**
390   * Returns a new range set consisting of the union of this range set and {@code other}.
391   *
392   * <p>This is essentially the same as {@code TreeRangeSet.create(this).addAll(other)} except it
393   * returns an {@code ImmutableRangeSet}.
394   *
395   * @since 21.0
396   */
397  public ImmutableRangeSet<C> union(RangeSet<C> other) {
398    return unionOf(Iterables.concat(asRanges(), other.asRanges()));
399  }
400
401  /**
402   * Returns a new range set consisting of the intersection of this range set and {@code other}.
403   *
404   * <p>This is essentially the same as {@code
405   * TreeRangeSet.create(this).removeAll(other.complement())} except it returns an {@code
406   * ImmutableRangeSet}.
407   *
408   * @since 21.0
409   */
410  public ImmutableRangeSet<C> intersection(RangeSet<C> other) {
411    RangeSet<C> copy = TreeRangeSet.create(this);
412    copy.removeAll(other.complement());
413    return copyOf(copy);
414  }
415
416  /**
417   * Returns a new range set consisting of the difference of this range set and {@code other}.
418   *
419   * <p>This is essentially the same as {@code TreeRangeSet.create(this).removeAll(other)} except it
420   * returns an {@code ImmutableRangeSet}.
421   *
422   * @since 21.0
423   */
424  public ImmutableRangeSet<C> difference(RangeSet<C> other) {
425    RangeSet<C> copy = TreeRangeSet.create(this);
426    copy.removeAll(other);
427    return copyOf(copy);
428  }
429
430  /**
431   * Returns a list containing the nonempty intersections of {@code range} with the ranges in this
432   * range set.
433   */
434  private ImmutableList<Range<C>> intersectRanges(final Range<C> range) {
435    if (ranges.isEmpty() || range.isEmpty()) {
436      return ImmutableList.of();
437    } else if (range.encloses(span())) {
438      return ranges;
439    }
440
441    final int fromIndex;
442    if (range.hasLowerBound()) {
443      fromIndex =
444          SortedLists.binarySearch(
445              ranges,
446              Range.<C>upperBoundFn(),
447              range.lowerBound,
448              KeyPresentBehavior.FIRST_AFTER,
449              KeyAbsentBehavior.NEXT_HIGHER);
450    } else {
451      fromIndex = 0;
452    }
453
454    int toIndex;
455    if (range.hasUpperBound()) {
456      toIndex =
457          SortedLists.binarySearch(
458              ranges,
459              Range.<C>lowerBoundFn(),
460              range.upperBound,
461              KeyPresentBehavior.FIRST_PRESENT,
462              KeyAbsentBehavior.NEXT_HIGHER);
463    } else {
464      toIndex = ranges.size();
465    }
466    final int length = toIndex - fromIndex;
467    if (length == 0) {
468      return ImmutableList.of();
469    } else {
470      return new ImmutableList<Range<C>>() {
471        @Override
472        public int size() {
473          return length;
474        }
475
476        @Override
477        public Range<C> get(int index) {
478          checkElementIndex(index, length);
479          if (index == 0 || index == length - 1) {
480            return ranges.get(index + fromIndex).intersection(range);
481          } else {
482            return ranges.get(index + fromIndex);
483          }
484        }
485
486        @Override
487        boolean isPartialView() {
488          return true;
489        }
490      };
491    }
492  }
493
494  /** Returns a view of the intersection of this range set with the given range. */
495  @Override
496  public ImmutableRangeSet<C> subRangeSet(Range<C> range) {
497    if (!isEmpty()) {
498      Range<C> span = span();
499      if (range.encloses(span)) {
500        return this;
501      } else if (range.isConnected(span)) {
502        return new ImmutableRangeSet<C>(intersectRanges(range));
503      }
504    }
505    return of();
506  }
507
508  /**
509   * Returns an {@link ImmutableSortedSet} containing the same values in the given domain
510   * {@linkplain RangeSet#contains contained} by this range set.
511   *
512   * <p><b>Note:</b> {@code a.asSet(d).equals(b.asSet(d))} does not imply {@code a.equals(b)}! For
513   * example, {@code a} and {@code b} could be {@code [2..4]} and {@code (1..5)}, or the empty
514   * ranges {@code [3..3)} and {@code [4..4)}.
515   *
516   * <p><b>Warning:</b> Be extremely careful what you do with the {@code asSet} view of a large
517   * range set (such as {@code ImmutableRangeSet.of(Range.greaterThan(0))}). Certain operations on
518   * such a set can be performed efficiently, but others (such as {@link Set#hashCode} or {@link
519   * Collections#frequency}) can cause major performance problems.
520   *
521   * <p>The returned set's {@link Object#toString} method returns a shorthand form of the set's
522   * contents, such as {@code "[1..100]}"}.
523   *
524   * @throws IllegalArgumentException if neither this range nor the domain has a lower bound, or if
525   *     neither has an upper bound
526   */
527  public ImmutableSortedSet<C> asSet(DiscreteDomain<C> domain) {
528    checkNotNull(domain);
529    if (isEmpty()) {
530      return ImmutableSortedSet.of();
531    }
532    Range<C> span = span().canonical(domain);
533    if (!span.hasLowerBound()) {
534      // according to the spec of canonical, neither this ImmutableRangeSet nor
535      // the range have a lower bound
536      throw new IllegalArgumentException(
537          "Neither the DiscreteDomain nor this range set are bounded below");
538    } else if (!span.hasUpperBound()) {
539      try {
540        domain.maxValue();
541      } catch (NoSuchElementException e) {
542        throw new IllegalArgumentException(
543            "Neither the DiscreteDomain nor this range set are bounded above");
544      }
545    }
546
547    return new AsSet(domain);
548  }
549
550  private final class AsSet extends ImmutableSortedSet<C> {
551    private final DiscreteDomain<C> domain;
552
553    AsSet(DiscreteDomain<C> domain) {
554      super(Ordering.natural());
555      this.domain = domain;
556    }
557
558    @CheckForNull private transient Integer size;
559
560    @Override
561    public int size() {
562      // racy single-check idiom
563      Integer result = size;
564      if (result == null) {
565        long total = 0;
566        for (Range<C> range : ranges) {
567          total += ContiguousSet.create(range, domain).size();
568          if (total >= Integer.MAX_VALUE) {
569            break;
570          }
571        }
572        result = size = Ints.saturatedCast(total);
573      }
574      return result.intValue();
575    }
576
577    @Override
578    public UnmodifiableIterator<C> iterator() {
579      return new AbstractIterator<C>() {
580        final Iterator<Range<C>> rangeItr = ranges.iterator();
581        Iterator<C> elemItr = Iterators.emptyIterator();
582
583        @Override
584        @CheckForNull
585        protected C computeNext() {
586          while (!elemItr.hasNext()) {
587            if (rangeItr.hasNext()) {
588              elemItr = ContiguousSet.create(rangeItr.next(), domain).iterator();
589            } else {
590              return endOfData();
591            }
592          }
593          return elemItr.next();
594        }
595      };
596    }
597
598    @Override
599    @GwtIncompatible("NavigableSet")
600    public UnmodifiableIterator<C> descendingIterator() {
601      return new AbstractIterator<C>() {
602        final Iterator<Range<C>> rangeItr = ranges.reverse().iterator();
603        Iterator<C> elemItr = Iterators.emptyIterator();
604
605        @Override
606        @CheckForNull
607        protected C computeNext() {
608          while (!elemItr.hasNext()) {
609            if (rangeItr.hasNext()) {
610              elemItr = ContiguousSet.create(rangeItr.next(), domain).descendingIterator();
611            } else {
612              return endOfData();
613            }
614          }
615          return elemItr.next();
616        }
617      };
618    }
619
620    ImmutableSortedSet<C> subSet(Range<C> range) {
621      return subRangeSet(range).asSet(domain);
622    }
623
624    @Override
625    ImmutableSortedSet<C> headSetImpl(C toElement, boolean inclusive) {
626      return subSet(Range.upTo(toElement, BoundType.forBoolean(inclusive)));
627    }
628
629    @Override
630    ImmutableSortedSet<C> subSetImpl(
631        C fromElement, boolean fromInclusive, C toElement, boolean toInclusive) {
632      if (!fromInclusive && !toInclusive && Range.compareOrThrow(fromElement, toElement) == 0) {
633        return ImmutableSortedSet.of();
634      }
635      return subSet(
636          Range.range(
637              fromElement, BoundType.forBoolean(fromInclusive),
638              toElement, BoundType.forBoolean(toInclusive)));
639    }
640
641    @Override
642    ImmutableSortedSet<C> tailSetImpl(C fromElement, boolean inclusive) {
643      return subSet(Range.downTo(fromElement, BoundType.forBoolean(inclusive)));
644    }
645
646    @Override
647    public boolean contains(@CheckForNull Object o) {
648      if (o == null) {
649        return false;
650      }
651      try {
652        @SuppressWarnings("unchecked") // we catch CCE's
653        C c = (C) o;
654        return ImmutableRangeSet.this.contains(c);
655      } catch (ClassCastException e) {
656        return false;
657      }
658    }
659
660    @Override
661    int indexOf(@CheckForNull Object target) {
662      if (contains(target)) {
663        @SuppressWarnings("unchecked") // if it's contained, it's definitely a C
664        C c = (C) requireNonNull(target);
665        long total = 0;
666        for (Range<C> range : ranges) {
667          if (range.contains(c)) {
668            return Ints.saturatedCast(total + ContiguousSet.create(range, domain).indexOf(c));
669          } else {
670            total += ContiguousSet.create(range, domain).size();
671          }
672        }
673        throw new AssertionError("impossible");
674      }
675      return -1;
676    }
677
678    @Override
679    ImmutableSortedSet<C> createDescendingSet() {
680      return new DescendingImmutableSortedSet<C>(this);
681    }
682
683    @Override
684    boolean isPartialView() {
685      return ranges.isPartialView();
686    }
687
688    @Override
689    public String toString() {
690      return ranges.toString();
691    }
692
693    @Override
694    @J2ktIncompatible // serialization
695    Object writeReplace() {
696      return new AsSetSerializedForm<C>(ranges, domain);
697    }
698
699    @J2ktIncompatible // java.io.ObjectInputStream
700    private void readObject(ObjectInputStream stream) throws InvalidObjectException {
701      throw new InvalidObjectException("Use SerializedForm");
702    }
703  }
704
705  private static class AsSetSerializedForm<C extends Comparable> implements Serializable {
706    private final ImmutableList<Range<C>> ranges;
707    private final DiscreteDomain<C> domain;
708
709    AsSetSerializedForm(ImmutableList<Range<C>> ranges, DiscreteDomain<C> domain) {
710      this.ranges = ranges;
711      this.domain = domain;
712    }
713
714    Object readResolve() {
715      return new ImmutableRangeSet<C>(ranges).asSet(domain);
716    }
717  }
718
719  /**
720   * Returns {@code true} if this immutable range set's implementation contains references to
721   * user-created objects that aren't accessible via this range set's methods. This is generally
722   * used to determine whether {@code copyOf} implementations should make an explicit copy to avoid
723   * memory leaks.
724   */
725  boolean isPartialView() {
726    return ranges.isPartialView();
727  }
728
729  /** Returns a new builder for an immutable range set. */
730  public static <C extends Comparable<?>> Builder<C> builder() {
731    return new Builder<C>();
732  }
733
734  /**
735   * A builder for immutable range sets.
736   *
737   * @since 14.0
738   */
739  public static class Builder<C extends Comparable<?>> {
740    private final List<Range<C>> ranges;
741
742    public Builder() {
743      this.ranges = Lists.newArrayList();
744    }
745
746    // TODO(lowasser): consider adding union, in addition to add, that does allow overlap
747
748    /**
749     * Add the specified range to this builder. Adjacent ranges are permitted and will be merged,
750     * but overlapping ranges will cause an exception when {@link #build()} is called.
751     *
752     * @throws IllegalArgumentException if {@code range} is empty
753     */
754    @CanIgnoreReturnValue
755    public Builder<C> add(Range<C> range) {
756      checkArgument(!range.isEmpty(), "range must not be empty, but was %s", range);
757      ranges.add(range);
758      return this;
759    }
760
761    /**
762     * Add all ranges from the specified range set to this builder. Adjacent ranges are permitted
763     * and will be merged, but overlapping ranges will cause an exception when {@link #build()} is
764     * called.
765     */
766    @CanIgnoreReturnValue
767    public Builder<C> addAll(RangeSet<C> ranges) {
768      return addAll(ranges.asRanges());
769    }
770
771    /**
772     * Add all of the specified ranges to this builder. Adjacent ranges are permitted and will be
773     * merged, but overlapping ranges will cause an exception when {@link #build()} is called.
774     *
775     * @throws IllegalArgumentException if any inserted ranges are empty
776     * @since 21.0
777     */
778    @CanIgnoreReturnValue
779    public Builder<C> addAll(Iterable<Range<C>> ranges) {
780      for (Range<C> range : ranges) {
781        add(range);
782      }
783      return this;
784    }
785
786    @CanIgnoreReturnValue
787    Builder<C> combine(Builder<C> builder) {
788      addAll(builder.ranges);
789      return this;
790    }
791
792    /**
793     * Returns an {@code ImmutableRangeSet} containing the ranges added to this builder.
794     *
795     * @throws IllegalArgumentException if any input ranges have nonempty overlap
796     */
797    public ImmutableRangeSet<C> build() {
798      ImmutableList.Builder<Range<C>> mergedRangesBuilder =
799          new ImmutableList.Builder<>(ranges.size());
800      Collections.sort(ranges, Range.<C>rangeLexOrdering());
801      PeekingIterator<Range<C>> peekingItr = Iterators.peekingIterator(ranges.iterator());
802      while (peekingItr.hasNext()) {
803        Range<C> range = peekingItr.next();
804        while (peekingItr.hasNext()) {
805          Range<C> nextRange = peekingItr.peek();
806          if (range.isConnected(nextRange)) {
807            checkArgument(
808                range.intersection(nextRange).isEmpty(),
809                "Overlapping ranges not permitted but found %s overlapping %s",
810                range,
811                nextRange);
812            range = range.span(peekingItr.next());
813          } else {
814            break;
815          }
816        }
817        mergedRangesBuilder.add(range);
818      }
819      ImmutableList<Range<C>> mergedRanges = mergedRangesBuilder.build();
820      if (mergedRanges.isEmpty()) {
821        return of();
822      } else if (mergedRanges.size() == 1
823          && Iterables.getOnlyElement(mergedRanges).equals(Range.all())) {
824        return all();
825      } else {
826        return new ImmutableRangeSet<C>(mergedRanges);
827      }
828    }
829  }
830
831  private static final class SerializedForm<C extends Comparable> implements Serializable {
832    private final ImmutableList<Range<C>> ranges;
833
834    SerializedForm(ImmutableList<Range<C>> ranges) {
835      this.ranges = ranges;
836    }
837
838    Object readResolve() {
839      if (ranges.isEmpty()) {
840        return of();
841      } else if (ranges.equals(ImmutableList.of(Range.all()))) {
842        return all();
843      } else {
844        return new ImmutableRangeSet<C>(ranges);
845      }
846    }
847  }
848
849  @J2ktIncompatible // java.io.ObjectInputStream
850  Object writeReplace() {
851    return new SerializedForm<C>(ranges);
852  }
853
854  @J2ktIncompatible // java.io.ObjectInputStream
855  private void readObject(ObjectInputStream stream) throws InvalidObjectException {
856    throw new InvalidObjectException("Use SerializedForm");
857  }
858}